Investments (Detail) - Securities Previously Classified as CDOs (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Weighted Average Life	4.29	4.37
Amortized Cost	$ 17,924	$ 40,666
Fair Value	26,634	53,303
Average Rating	B	BB
Change in Fair Value During the Six months ended June 30, 2011 and Six month ended December 31 2010	(7,425)	12,637
SyntheticCDO [Member]
Weighted Average Life	1.80	3.87
Amortized Cost	8,942	32,175
Fair Value	10,880	41,105
Average Rating	B	BB
Change in Fair Value During the Six months ended June 30, 2011 and Six month ended December 31 2010	(8,392)	8,930
CDO Squared [Member]
Weighted Average Life	6.00	6.04
Amortized Cost	8,982	8,491
Fair Value	15,754	12,198
Average Rating	B	B
Change in Fair Value During the Six months ended June 30, 2011 and Six month ended December 31 2010	$ 967	$ 3,707