Schedule II - Condensed Financial Information of Registrant (Statements of Income (Parent Company)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	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, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Income Statements, Captions [Line Items]
Net investment gains (losses)									$ 120,703	$ 154,488	$ 335,858
Other income									3,370	681	805
Total revenues	$ 1,976,074	$ 1,965,716	$ 2,023,384	$ 1,937,022	$ 1,951,586	$ 1,937,902	$ 1,910,916	$ 1,891,247	7,902,196	7,691,651	7,684,764
Operating costs and expense									7,049,276	6,879,557	6,911,994
Income before income taxes									852,920	812,094	772,770
Federal income taxes:
Net federal income tax expense (benefit)									(168,935)	(163,028)	(219,433)
Net income to common stockholders	$ 119,306	$ 165,208	$ 216,709	$ 180,722	$ 132,357	$ 161,920	$ 180,075	$ 166,397	681,944	640,749	549,094
Dividends from subsidiaries									416,027	639,477	694,462
Parent Company
Condensed Income Statements, Captions [Line Items]
Management fees and investment income including dividends from subsidiaries of$416,027, $639,477, and $694,462 for the years ended December 31, 2019, 2018 and 2017, respectively									470,773	697,687	738,923
Net investment gains (losses)									850	(1,685)	(4,286)
Other income									117	530	805
Total revenues									471,740	696,532	735,442
Operating costs and expense									204,812	191,873	182,145
Interest expense									148,282	155,082	146,929
Income before income taxes									118,646	349,577	406,368
Federal income taxes:
Federal income taxes provided by subsidiaries on a separate return basis									207,647	409,439	115,597
Federal income tax expense on a consolidated return basis									(141,190)	(113,138)	(195,261)
Net federal income tax expense (benefit)									66,457	296,301	(79,664)
Income before undistributed equity in net income of subsidiaries									185,103	645,878	326,704
Equity in undistributed net income (loss) of subsidiaries									496,841	(5,129)	222,390
Net income to common stockholders									$ 681,944	$ 640,749	$ 549,094