Rollforward of Other-than-temporary Impairment Credit-related Losses Recognized in Income, Fixed-maturity Securities Still Held (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Impairments [Abstract]
Cumulative other-than-temporary impairment, credit losses for securities still held	$ 15,035	$ 24,083	$ 15,035	$ 24,083	$ 15,970	$ 17,403	$ 23,221	$ 24,460
Additions for other-than-temporary impaired securities where no credit losses were recognized prior to the beginning of the period	0	133	10	137
Additions for other-than-temporary impaired securities where credit losses have been recognized prior to the beginning of the period	3	848	333	1,172
Reductions due to sales, maturities or calls of credit impaired securities	$ (938)	$ (119)	$ (2,711)	$ (1,686)