Consolidated Statements of Cash Flows (USD $) In Thousands	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Operating activities
Net income (loss)	$ 493,707	$ 84,822	$ 68,883
Adjustments to reconcile net income (loss) to net cash flows provided by operating activities:
Non-cash interest and operating expenses	24,352	16,250	16,328
Net amortization of premium on fixed maturity securities	46,338	21,997	2,397
Provision (benefit) for deferred income taxes	80,750	(185,143)	43,116
Net realized investment losses (gains)	1,994	32,662	69,801
Net unrealized losses (gains) on credit derivatives	155,106	337,810	(38,034)
Fair value loss (gain) on committed capital securities	(9,195)	122,940	(42,746)
Goodwill and settlements of pre-existing relationship		23,341
Non-cash items in other income	4,314	(20,691)
Change in deferred acquisition costs	2,156	31,646	(29,318)
Change in premiums receivable, net of ceding commissions	376,478	119,663	12,059
Change in ceded unearned premium reserves	256,257	203,063	(5,326)
Change in unearned premium reserve	(1,278,206)	(731,114)	346,543
Change in loss and loss adjustment expense reserve, net	(470,839)	1,186	16,583
Change in current income taxes	(87,165)	175,873	(22,046)
Other changes in credit derivatives assets and liabilities, net	33,652	15,802	7,197
Change in financial guaranty variable interest entities' assets and liabilities, net	540,691
Other	(41,201)	29,063	(18,448)
Net cash flows provided by (used in) operating activities	129,189	279,170	426,989
Fixed maturity securities:
Purchases	(2,461,692)	(2,287,668)	(1,272,024)
Sales	1,063,581	1,519,300	532,144
Maturities	994,360	217,895	11,730
Net sales (purchases) of short-term investments	613,267	(397,100)	78,535
Net proceeds from paydowns on financial guaranty variable interest entities' assets	423,997
Cash paid to acquire Assured Guaranty Municipal Holdings Inc., net of cash acquired		(458,998)
Other	19,786	9,350
Net cash flows provided by (used in) investing activities	653,299	(1,397,221)	(649,615)
Financing activities
Net proceeds from issuance of common stock		1,022,096	248,967
Net proceeds from issuance of equity units		167,972
Dividends paid	(33,190)	(22,332)	(16,015)
Repurchases of common stock	(10,457)	(3,676)
Share activity under option and incentive plans	(2,062)	(667)	(3,632)
Tax benefit for stock options exercised	28	(16)	16
Net paydowns of financial guaranty variable interest entities' liabilities	(650,862)
Repayment of long-term debt	(20,891)	(14,823)
Net cash flows provided by (used in) financing activities	(717,434)	1,148,554	229,336
Effect of exchange rate changes	(798)	1,325	(2,453)
Increase in cash	64,256	31,828	4,257
Cash at beginning of year	44,133	12,305	8,048
Cash at end of year	108,389	44,133	12,305
Cash paid (received) during the period for:
Income taxes	39,215	27,849	18,743
Interest	$ 90,314	$ 56,418	$ 23,600