Consolidated Balance Sheets (USD $) In Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2010
Investment portfolio:
Fixed maturity securities, available-for-sale, at fair value (amortized cost of $9,368,735 and $9,274,718)	$ 9,459,814	$ 9,402,287
Short term investments, at fair value	813,392	1,055,567
Other invested assets	264,517	283,032
Total investment portfolio	10,537,723	10,740,886
Cash	111,587	108,389
Premiums receivable, net of ceding commissions payable	1,118,033	1,167,587
Ceded unearned premium reserve	794,300	821,819
Deferred acquisition costs	235,982	239,805
Reinsurance recoverable on unpaid losses	18,641	22,255
Salvage and subrogation recoverable	1,056,961	1,032,369
Credit derivative assets	619,303	592,898
Deferred tax asset, net	1,031,688	1,259,125
Current income tax receivable	159,571
Financial guaranty variable interest entities' assets, at fair value	3,679,025	3,657,481
Other assets	221,855	199,305
Total assets	19,584,669	19,841,919
Liabilities and shareholders' equity
Unearned premium reserve	6,637,213	6,972,894
Loss and loss adjustment expense reserve	419,592	574,369
Reinsurance balances payable, net	268,221	274,431
Long-term debt	1,049,708	1,052,936
Credit derivative liabilities	2,759,326	2,462,831
Current income tax payable		93,020
Financial guaranty variable interest entities' liabilities with recourse, at fair value	2,874,183	3,030,908
Financial guaranty variable interest entities' liabilities without recourse, at fair value	1,373,006	1,337,214
Other liabilities	359,367	309,862
Total liabilities	15,740,616	16,108,465
Commitments and contingencies (See Note 13)
Common stock ($0.01 par value, 500,000,000 shares authorized; 184,044,597 and 183,744,655 shares issued and outstanding in 2011 and 2010)	1,840	1,837
Additional paid-in capital	2,589,197	2,585,423
Retained earnings	1,164,703	1,032,445
Accumulated other comprehensive income, net of tax provision (benefit) of $8,345 and $18,341	86,313	111,749
Deferred equity compensation (181,818 shares)	2,000	2,000
Total shareholders' equity	3,844,053	3,733,454
Total liabilities and shareholders' equity	$ 19,584,669	$ 19,841,919