Investments (Details 3) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Fixed maturities, short-term and other investments and cash equivalents
Gross realized gains	$ 13,032	$ 15,120	$ 28,797	$ 27,885
Gross realized (losses)	(1,480)	(2,679)	(10,866)	(4,046)
Net realized gains on investments	11,552	12,441	17,931	23,839
Net unrealized gains (losses) on investments	18,526	41,640	5,698	57,053
Net unrealized gains (losses) on securities lending	11	(6)	41	(1,020)
Total net realized gains and change in net unrealized gains on investments	30,078	54,081	23,629	80,892
Investments excluding securities lending [Member]
Fixed maturities, short-term and other investments and cash equivalents
Net unrealized gains (losses) on investments	$ 18,515	$ 41,646	$ 5,657	$ 58,073