Investments - Credit loss rollforward (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	Mar. 31, 2012	Mar. 31, 2011
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance			$ 783	$ 1,387	$ 783	$ 767
Amounts related to credit loss for which an OTTI charge was not previously recognized	0	0	0	31
Increases to the amount related to credit loss for which OTTI was previously recognized	0	0	0	0
Realized losses for securities sold	0	16	0	(635)
Ending balance	$ 783	$ 783	$ 783	$ 783	$ 783	$ 767