Schedule II Condensed Financial Information of Registrant - Condensed Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Net investment income													$ 357,596	$ 365,064	$ 376,507
Net investment gains (losses)													(2,289)	153,340	(12,543)
Total revenues	$ 352,344	$ 337,080	$ 314,459	$ 306,558	$ 331,376	$ 334,418	$ 451,478	$ 313,213	$ 278,535	$ 311,318	$ 306,257	$ 295,489	1,310,441	1,430,485	1,191,599
Expenses
Interest expense													15,215	15,577	13,001
Total benefits, losses and expenses													1,150,858	1,194,036	1,172,062
Income tax benefit													26,268	52,006	1,194
Net income	$ 47,791	$ 36,474	$ 30,578	$ 18,472	$ 33,001	$ 25,454	$ 93,822	$ 32,166	$ (20,257)	$ 12,528	$ 5,917	$ 20,155	133,315	184,443	18,343
Parent company
Revenues
Net investment income													(174)	(135)	100
Net investment gains (losses)													0	0	0
Total revenues													(174)	(135)	100
Expenses
Interest expense													14,771	14,272	11,892
Other													5,750	12,632	10,898
Total benefits, losses and expenses													20,521	26,904	22,790
Loss before income tax benefit and equity in net earnings of subsidiaries													(20,695)	(27,039)	(22,690)
Income tax benefit													(5,307)	(6,029)	(4,723)
Loss before equity in net earnings of subsidiaries													(15,388)	(21,010)	(17,967)
Equity in net earnings of subsidiaries													148,703	205,453	36,310
Net income													$ 133,315	$ 184,443	$ 18,343