Fair Value Measurements Other Long-Term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment related gains (losses), net	$ 760	$ (10,291)	$ 10,991
Other Long-Term Investments	82,725	69,558
Limited Partnership Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment related gains (losses), net	$ 900	$ (9,700)	$ 7,500
Middle market
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range (In years)	4 years	5 years
Global equity market
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range (In years)	0 years	0 years
Late-stage growth | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range (In years)	4 years	5 years
Late-stage growth | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range (In years)	6 years	7 years
Infrastructure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range (In years)	10 years	11 years
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	$ 82,460	$ 66,846
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds | Unfunded Loan Commitment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	27,299	28,562
Fair Value Measured at Net Asset Value Per Share | Middle market
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	34,858	33,234
Fair Value Measured at Net Asset Value Per Share | Middle market | Unfunded Loan Commitment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	3,452	6,011
Fair Value Measured at Net Asset Value Per Share | Global equity market
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	10,345	9,037
Fair Value Measured at Net Asset Value Per Share | Global equity market | Unfunded Loan Commitment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	0	0
Fair Value Measured at Net Asset Value Per Share | Late-stage growth
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	20,524	16,892
Fair Value Measured at Net Asset Value Per Share | Late-stage growth | Unfunded Loan Commitment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	14,271	18,444
Fair Value Measured at Net Asset Value Per Share | Infrastructure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	16,733	7,683
Fair Value Measured at Net Asset Value Per Share | Infrastructure | Unfunded Loan Commitment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Long-Term Investments	$ 9,576	$ 4,107