Investments - Credit loss rollforward (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 783	$ 1,418	$ 783	$ 1,387
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	(651)	0	(651)
Ending balance	$ 783	$ 767	$ 783	$ 767