Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 109,597	$ 108,718	$ 290,464	$ 233,919
Other comprehensive income (loss), net of tax:
Net realized and unrealized holding gains (losses) on investments	43,484	(54,049)	72,529	(90,109)
Reclassification for net losses on investments included in earnings	(191)	(405)	6,428	6,185
Noncredit-related impairment losses on securities not expected to be sold	(703)	(25,589)	(16,006)	(26,318)
Accretion of securities with noncredit-related impairment losses not expected to be sold	192	32	724	131
Net unrealized losses on derivative instruments	(1,373)	(4,332)	(6,329)	(17,427)
Other comprehensive income (loss)	41,409	(84,343)	57,346	(127,538)
Comprehensive income	151,006	24,375	347,810	106,381
Comprehensive loss applicable to noncontrolling interests	(254)	(375)	(800)	(866)
Comprehensive income applicable to controlling interest	$ 151,260	$ 24,750	$ 348,610	$ 107,247