Fair Value Measurements (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	$ 63,927,000		$ 57,399,000
Investment related gains (losses), net	$ (582,000)	$ 292,000
Limited Partnership Funds - Middle Market
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Maturity Timeframe of Other Long-Term Investments	9 years		10 years
Limited Partnership Funds - Global
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Maturity Timeframe of Other Long-Term Investments	0 years		0 years
Limited Partnership Funds - Late-Stage Growth
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Maturity Timeframe of Other Long-Term Investments	6 years		6 years
Limited Partnership Funds - Infrastructure
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Maturity Timeframe of Other Long-Term Investments	11 years		12 years
Limited Partnership Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	$ 0		$ 0
Investment related gains (losses), net	(800,000)
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Middle Market
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	27,336,000		21,947,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Middle Market | Unfunded Loan Commitment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	13,593,000		18,712,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Global
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	9,890,000		10,607,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Global | Unfunded Loan Commitment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	0		0
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Late-Stage Growth
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	21,564,000		20,468,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Late-Stage Growth | Unfunded Loan Commitment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	7,256,000		4,459,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Infrastructure
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	3,774,000		3,016,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds - Infrastructure | Unfunded Loan Commitment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	15,970,000		16,653,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	62,564,000		56,038,000
Fair Value Measured at Net Asset Value Per Share | Limited Partnership Funds [Member] | Unfunded Loan Commitment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	$ 36,819,000		$ 39,824,000