Restatement of Previously Issued Financial Statements (Details 4) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Net cash flows provided by (used in) operating activities	$ 631,946	$ (217,674)
Fixed maturity securities:
Purchases	(1,349,745)	(1,166,379)
Sales	685,980	780,818
Maturities	325,750	488,552
Net sales (purchases) of short-term investments	(49,901)	248,780
Net proceeds from paydowns on financial guaranty variable interest entities' assets	423,977	217,329
Other	8,696	8,317
Net cash flows provided by (used in) investing activities	44,757	577,417
Financing activities
Dividends paid	(16,577)	(16,613)
Repurchases of common stock		(10,457)
Share activity under option and incentive plans	(2,652)	(2,233)
Net paydowns of financial guaranty variable interest entities' liabilities	(593,294)	(259,367)
Repayment of long-term debt	(10,294)	(10,850)
Net cash flows provided by (used in) financing activities	(622,817)	(299,520)
Effect of foreign exchange rate changes	3,215	(3,090)
Increase in cash	57,101	57,133
Cash at beginning of period	108,389	44,133
Cash at end of period	165,490	101,266
As Previously Filed
Net cash flows provided by (used in) operating activities	614,400	(249,500)
Fixed maturity securities:
Purchases	(1,349,700)	(1,166,300)
Sales	686,000	780,800
Maturities	326,900	488,600
Net sales (purchases) of short-term investments	(38,700)	276,600
Net proceeds from paydowns on financial guaranty variable interest entities' assets	424,000	217,300
Other	8,700	8,300
Net cash flows provided by (used in) investing activities	57,200	605,300
Financing activities
Dividends paid	(16,600)	(16,600)
Repurchases of common stock		(10,500)
Share activity under option and incentive plans	(2,600)	(2,300)
Net paydowns of financial guaranty variable interest entities' liabilities	(593,300)	(259,400)
Repayment of long-term debt	(10,300)	(10,800)
Net cash flows provided by (used in) financing activities	(622,800)	(299,600)
Effect of foreign exchange rate changes	3,200	(3,100)
Increase in cash	52,000	53,100
Cash at beginning of period	107,200	44,100
Cash at end of period	159,200	97,200
FG VIE Eliminations
Net cash flows provided by (used in) operating activities	17,500	31,900
Fixed maturity securities:
Maturities	(1,200)
Net sales (purchases) of short-term investments	(11,200)	(27,900)
Net cash flows provided by (used in) investing activities	(12,400)	(27,900)
Financing activities
Increase in cash	5,100	4,000
Cash at beginning of period	1,200
Cash at end of period	$ 6,300	$ 4,000