Fair Values of Financial Instruments - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	$ 7,611,633	$ 9,068,946
Debt securities, trading	1,065,993	1,077,438
Equity securities	22,076	28,217
Derivatives, index options	$ 23,669	$ 101,622
DerivativeLiabilityStatementOfFinancialPositionExtensibleEnumerationNotDisclosedFlag	Policyholder account balances (a)	Policyholder account balances (a)
Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	$ 7,611,633	$ 9,068,946
Debt securities, trading	1,065,993	1,077,438
Equity securities	22,076	28,217
Mortgage loans	19,334	8,469
Derivatives, index options	23,669	101,622
Short-term investments	3,937
Total assets	8,746,642	10,284,692
Policyholder account balances	62,258	142,761
Other liabilities	(314,413)	(76,856)
Total liabilities	(252,155)	65,905
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	0	0
Debt securities, trading	0	0
Equity securities	18,407	23,795
Mortgage loans	0	0
Derivatives, index options	0	0
Short-term investments	0
Level 1 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	0	0
Debt securities, trading	0	0
Equity securities	18,407	23,795
Mortgage loans	0	0
Derivatives, index options	0	0
Short-term investments	0
Total assets	18,407	23,795
Policyholder account balances	0	0
Other liabilities	0	0
Total liabilities	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	7,148,837	8,741,984
Debt securities, trading	942,756	1,002,616
Equity securities	3,669	4,422
Mortgage loans	0	0
Derivatives, index options	0	0
Short-term investments	3,937
Level 2 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	7,148,838	8,741,984
Debt securities, trading	942,756	1,002,616
Equity securities	3,669	4,422
Mortgage loans	0	0
Derivatives, index options	0	0
Short-term investments	3,937
Total assets	8,099,200	9,749,022
Policyholder account balances	0	0
Other liabilities	(324,712)	(84,725)
Total liabilities	(324,712)	(84,725)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	462,796	326,962
Debt securities, trading	123,237	74,822
Equity securities	0	0
Mortgage loans	457,873	513,246
Derivatives, index options	23,669	101,622
Short-term investments	0
Total assets	119,006	223,359
Total liabilities	82,800	150,630
Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	462,795	326,962
Debt securities, trading	123,237	74,822
Equity securities	0	0
Mortgage loans	19,334	8,469
Derivatives, index options	23,669	101,622
Short-term investments	0
Total assets	629,035	511,875
Policyholder account balances	62,258	142,761
Other liabilities	10,299	7,869
Total liabilities	$ 72,557	$ 150,630