6. Derivative Instruments Realized Gains (Losses) (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
Derivative Instruments Realized Gains Losses Details
Interest rate swaps	$ 1,783	$ 4,822	$ 492	$ 4,276
Variance swaps	876	(278)	(4,512)	(1,653)
Swaptions	(40)	(217)	(194)	(406)
Put options	7,851	2,275	(3,883)	(5,000)
Call options	(9,843)	(5,006)	22	(3,283)
Equity futures	5,221	(126)	(9,605)	(5,805)
Total derivative instrument realized gains (losses) recognized in earnings	$ 5,848	$ 1,470	$ (17,680)	$ (11,871)