Annual report pursuant to Section 13 and 15(d)

DEFINED CONTRIBUTION AND PENSION PLANS - Allocation of Plan Assets (Details)

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DEFINED CONTRIBUTION AND PENSION PLANS - Allocation of Plan Assets (Details) - USD ($)
$ in Thousands
Dec. 31, 2023
Dec. 31, 2022
Mar. 31, 2022
Mar. 31, 2021
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments $ 366,630 $ 347,520 $ 511,786 $ 534,768
Fair Value, Inputs, Level 1, 2 and 3        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 329,403 304,937    
Fair Value, Inputs, Level 1, 2 and 3 | Cash and cash equivalents        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 20,524 13,352    
Fair Value, Inputs, Level 1, 2 and 3 | Equity investments - UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 510 962    
Fair Value, Inputs, Level 1, 2 and 3 | Equity investments - non-UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 2,932 2,165    
Fair Value, Inputs, Level 1, 2 and 3 | Insurance linked securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 382 25,141    
Fair Value, Inputs, Level 1, 2 and 3 | Liquid credit        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 49,334 7,819    
Fair Value, Inputs, Level 1, 2 and 3 | Alternative investments        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 52,521 42,222    
Fair Value, Inputs, Level 1, 2 and 3 | Diversified growth (absolute return) funds        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 892 722    
Fair Value, Inputs, Level 1, 2 and 3 | Government debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 90,127 102,488    
Fair Value, Inputs, Level 1, 2 and 3 | Corporate debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 1,402 1,203    
Fair Value, Inputs, Level 1, 2 and 3 | Insurance policy        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 110,779 108,863    
Level 1        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 13,257 9,262    
Level 1 | Cash and cash equivalents        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 6,629 3,729    
Level 1 | Equity investments - UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 510 962    
Level 1 | Equity investments - non-UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 2,932 2,165    
Level 1 | Insurance linked securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 1 | Liquid credit        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 1 | Alternative investments        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 1 | Diversified growth (absolute return) funds        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 892 722    
Level 1 | Government debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 892 481    
Level 1 | Corporate debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 1,402 1,203    
Level 1 | Insurance policy        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 2        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 204,985 161,671    
Level 2 | Cash and cash equivalents        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 13,895 9,623    
Level 2 | Equity investments - UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 2 | Equity investments - non-UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 2 | Insurance linked securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 2 | Liquid credit        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 49,334 7,819    
Level 2 | Alternative investments        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 52,521 42,222    
Level 2 | Diversified growth (absolute return) funds        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 2 | Government debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 89,235 102,007    
Level 2 | Corporate debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 2 | Insurance policy        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 111,161 134,004    
Level 3 | Cash and cash equivalents        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Equity investments - UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Equity investments - non-UK        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Insurance linked securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 382 25,141    
Level 3 | Liquid credit        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Alternative investments        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Diversified growth (absolute return) funds        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Government debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Corporate debt securities        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 0 0    
Level 3 | Insurance policy        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments 110,779 108,863    
Net asset value        
Defined Benefit Plan, Plan Assets, Category [Line Items]        
Total fair value investments $ 37,227 $ 42,583