Schedule II - Condensed Financial Information of Registrant (Statements of Income (Parent Company)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Income Statements, Captions [Line Items]
Other income									$ 1,308	$ 1,026	$ 2,564
Total revenues	1,784,428	1,840,605	1,796,989	1,706,906	1,696,679	1,634,124	1,570,962	1,506,769	7,128,928	6,408,534	5,823,554
Operating costs and expense									6,176,732	5,709,646	5,121,626
Income before income taxes									952,196	698,888	701,928
Federal income taxes:
Net expense									(302,593)	(193,587)	(191,285)
Net income to common stockholders	110,711	188,539	179,961	169,673	130,379	136,974	115,957	116,615	648,884	499,925	510,592
Dividends from subsidiaries									503,483	269,626	25,968
Parent Company
Condensed Income Statements, Captions [Line Items]
Management fees and investment income including dividends from subsidiaries of $503,483, $269,626, and $25,968 for the years ended December 31, 2014, 2013 and 2012, respectively									515,775	277,223	29,961
Net investment gains									5,487	24,550	71,130
Other income									450	223	271
Total revenues									521,712	301,996	101,362
Operating costs and expense									148,288	122,562	133,326
Interest expense									125,352	120,066	124,298
Income before income taxes									248,072	59,368	(156,262)
Federal income taxes:
Federal income taxes provided by subsidiaries on a separate return basis									366,721	225,845	132,379
Federal income tax expense on a consolidated return basis									(273,310)	(154,928)	(160,226)
Net expense									93,411	70,917	(27,847)
Income (loss) before undistributed equity in net income of subsidiaries									341,483	130,285	(184,109)
Equity in undistributed net income of subsidiaries									307,401	369,640	694,701
Net income to common stockholders									$ 648,884	$ 499,925	$ 510,592