Deferred Policy Acquisition Costs, Deferred Sales Inducements, and Value of Business Acquired (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning of year	$ 723,972	$ 841,704	$ 819,511
Deferrals	69,857	64,824	84,094
Amortization, excluding unlocking, net of interest	(107,917)	(117,748)	(115,721)
Unlocking	(22,358)	8,643	950
Adjustments related to unrealized gains (losses)	(261,186)	(73,451)	52,870
Reinsurance	(20,288)	0	0
Deferred policy acquisition costs, end of year	382,080	723,972	841,704
Movement in Deferred Sales Inducements [Roll Forward]
Deferred sales inducements, beginning of year	104,359	133,714	135,570
Deferrals	10,344	3,160	7,546
Amortization, excluding unlocking, net of interest	(22,808)	(19,714)	(21,569)
Unlocking	0	(641)	1,270
Adjustments related to unrealized gains (losses)	(43,557)	(12,160)	10,897
Reinsurance	(4,493)	0	0
Deferred sales inducements, end of year	43,845	104,359	133,714
Movement Analysis Of Value Of Business Acquired [Roll Forward]
VOBA, beginning of year	138,071	0
Business acquired	0	145,768
Other increase	35,125	0
Amortization, excluding unlocking	(10,228)	(7,697)
VOBA, end of year	162,968	$ 138,071	$ 0
Present Value of Future Insurance Profits, Amortization Expense [Abstract]
2021	9,707
2022	9,214
2023	8,786
2024	8,402
2025	$ 8,070

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