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Fair Value Measurements - Pension Plan Assets within Fair Value Hierarchy (Details) - USD ($)
$ in Thousands
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets $ 443,157 $ 477,728 $ 739,789
U.K Plan      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 156,142 174,873  
U.K Plan | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 2,272 2,411  
U.K Plan | Money Market Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 42,859 34,485  
U.K Plan | US Government Agencies Debt Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 72,913 91,256  
U.K Plan | Alternative strategies      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 34,998 37,246  
U.K Plan | Real Estate Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 3,100 9,475  
U.K Plan | Quoted Prices in Active Markets (Level 1)      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 8,697 4,856  
U.K Plan | Quoted Prices in Active Markets (Level 1) | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 2,272 2,411  
U.K Plan | Quoted Prices in Active Markets (Level 1) | Money Market Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Quoted Prices in Active Markets (Level 1) | US Government Agencies Debt Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Quoted Prices in Active Markets (Level 1) | Alternative strategies      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 6,425 2,445  
U.K Plan | Quoted Prices in Active Markets (Level 1) | Real Estate Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Significant Other Observable Inputs (Level 2)      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 142,518 160,542  
U.K Plan | Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Significant Other Observable Inputs (Level 2) | Money Market Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 42,859 34,485  
U.K Plan | Significant Other Observable Inputs (Level 2) | US Government Agencies Debt Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 72,913 91,256  
U.K Plan | Significant Other Observable Inputs (Level 2) | Alternative strategies      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 26,746 34,801  
U.K Plan | Significant Other Observable Inputs (Level 2) | Real Estate Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Significant Unobservable Inputs (Level 3)      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 4,927 9,475 11,255
U.K Plan | Significant Unobservable Inputs (Level 3) | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Significant Unobservable Inputs (Level 3) | Money Market Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Significant Unobservable Inputs (Level 3) | US Government Agencies Debt Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
U.K Plan | Significant Unobservable Inputs (Level 3) | Alternative strategies      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 1,827 0  
U.K Plan | Significant Unobservable Inputs (Level 3) | Real Estate Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 3,100 9,475  
US      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 271,412 281,159  
Other plan liabilities, net [1] (8,412) (1,409)  
Net Plan Assets 263,000 279,750  
US | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 3,482 4,847  
US | Short-term Investments      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 10,119 11,212  
US | United States Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 24,103 24,235  
US | International Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 15,394 12,844  
US | United States Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 186,648 185,641  
US | International Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 19,177 20,913  
US | Asset Categories Other      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 12,489 21,467  
US | Quoted Prices in Active Markets (Level 1)      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 55,266 63,417  
US | Quoted Prices in Active Markets (Level 1) | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 3,482 4,847  
US | Quoted Prices in Active Markets (Level 1) | Short-term Investments      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Quoted Prices in Active Markets (Level 1) | United States Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Quoted Prices in Active Markets (Level 1) | International Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Quoted Prices in Active Markets (Level 1) | United States Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 51,784 58,570  
US | Quoted Prices in Active Markets (Level 1) | International Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Quoted Prices in Active Markets (Level 1) | Asset Categories Other      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Other Observable Inputs (Level 2)      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 204,847 199,549  
US | Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Other Observable Inputs (Level 2) | Short-term Investments      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 10,119 11,212  
US | Significant Other Observable Inputs (Level 2) | United States Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 24,103 24,235  
US | Significant Other Observable Inputs (Level 2) | International Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 15,394 12,844  
US | Significant Other Observable Inputs (Level 2) | United States Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 134,864 127,071  
US | Significant Other Observable Inputs (Level 2) | International Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 19,177 20,913  
US | Significant Other Observable Inputs (Level 2) | Asset Categories Other      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 1,190 3,274  
US | Significant Unobservable Inputs (Level 3)      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 11,299 18,194 $ 19,268
US | Significant Unobservable Inputs (Level 3) | Cash and Cash Equivalents      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Unobservable Inputs (Level 3) | Short-term Investments      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Unobservable Inputs (Level 3) | United States Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Unobservable Inputs (Level 3) | International Equity Securities      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Unobservable Inputs (Level 3) | United States Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Unobservable Inputs (Level 3) | International Fixed Income Funds      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets 0 0  
US | Significant Unobservable Inputs (Level 3) | Asset Categories Other      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Total plan assets $ 11,299 $ 18,194  
[1] net amounts payable for unsettled security transactions.