Fair Value of Financial Instruments - Quantitative Information (Details) $ in Thousands	Jun. 30, 2022 USD ($) year	Dec. 31, 2021 USD ($) year
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	$ 8,160,952	$ 9,068,946
Derivatives, index options	6,071	101,622
Mortgage loans, at fair value	18,738	8,469
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	373,957	326,962
Derivatives, index options	6,071	101,622
Total assets	69,781	223,359
Total liabilities	54,674	150,630
Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale	44,972	113,268
Mortgage loans, at fair value	18,738	8,469
Broker prices | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	6,071	101,622
Deterministic cash flow model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Policyholder account balances	45,342	142,761
Black-Scholes model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share-based compensation	$ 9,332	$ 7,869
Expected volatility | Black-Scholes model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share based compensation, measurement input	0.3485	0.3505
Minimum | Discount rate | Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, available-for-sale, measurement input	0.0276	0.0240
Minimum | Implied volatility | Broker prices | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options, measurement input	0.1207	0.1176
Minimum | Spread | Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans, measurement input	0.0175	0.0100
Minimum | Projected option cost | Deterministic cash flow model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Policyholder account balances, measurement input	0.0000	0.0003
Minimum | Expected term | Black-Scholes model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share based compensation, measurement input | year	1.4	1.9
Maximum | Discount rate | Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, available-for-sale, measurement input	0.0614	0.0614
Maximum | Implied volatility | Broker prices | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options, measurement input	0.1840	0.1654
Maximum | Spread | Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans, measurement input	0.0275	0.0250
Maximum | Projected option cost | Deterministic cash flow model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Policyholder account balances, measurement input	0.0463	0.1449
Maximum | Expected term | Black-Scholes model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share based compensation, measurement input | year	9.5	10
Weighted-Average | Discount rate | Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, available-for-sale, measurement input	0.0458	0.0406
Weighted-Average | Implied volatility | Broker prices | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options, measurement input	0.1592	0.1455
Weighted-Average | Projected option cost | Deterministic cash flow model | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Policyholder account balances, measurement input	0.0016	0.0265