Summary of Investments (Details 7) (Fixed maturities, USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Fixed maturities
Bifurcated credit loss:
Beginning balance	$ 167,788	$ 167,961	$ 186,999	$ 186,999	$ 186,999
Additional credit loss recognized on securities previously impaired	173
Ending balance	$ 167,961	$ 167,961	$ 186,999	$ 186,999	$ 186,999