Investments (Details) - Credit loss impairments on fixed income securities (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
OTTI related to credit losses recognized in earnings
Balance, beginning of period	$ 299,720	$ 315,844	$ 333,379	$ 426,372
Credit loss impairment recognized in the current period on securities not previously impaired	2,805	10,478	8,683	26,384
Credit loss impairments previously recognized on securities which matured, paid down, prepaid or were sold during the period	(33,114)	(14,611)	(87,092)	(173,056)
Credit loss impairments previously recognized on securities impaired to fair value during the period	0	0	(12,891)	0
Additional credit loss impairments recognized in the current period on securities previously impaired	4,834	35,574	41,716	74,372
Accretion of credit loss impairments previously recognized due to an increase in cash flows expected to be collected	(2,773)	(4,010)	(12,323)	(10,797)
Balance, end of period	$ 271,472	$ 343,275	$ 271,472	$ 343,275