Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Investment portfolio:
Fixed maturity securities, available-for-sale, at fair value (amortized cost of $9,638,404 and $9,274,718)	$ 10,141,850	$ 9,402,287
Short term investments, at fair value	734,046	1,055,567
Other invested assets	222,869	283,032
Total investment portfolio	11,098,765	10,740,886
Cash	214,544	108,389
Premiums receivable, net of ceding commissions payable	1,002,852	1,167,587
Ceded unearned premium reserve	708,872	821,819
Deferred acquisition costs	231,875	239,805
Reinsurance recoverable on unpaid losses	69,300	22,255
Salvage and subrogation recoverable	367,718	1,032,369
Credit derivative assets	468,933	592,898
Deferred tax asset, net	770,943	1,259,125
Current income tax receivable	76,430
Financial guaranty variable interest entities' assets, at fair value	2,819,077	3,657,481
Other assets	262,222	199,305
Total assets	18,091,531	19,841,919
Liabilities and shareholders' equity
Unearned premium reserve	5,962,799	6,972,894
Loss and loss adjustment expense reserve	679,011	574,369
Reinsurance balances payable, net	170,982	274,431
Long-term debt	1,038,302	1,052,936
Credit derivative liabilities	1,772,803	2,462,831
Current income tax payable		93,020
Financial guaranty variable interest entities' liabilities with recourse, at fair value	2,396,945	3,030,908
Financial guaranty variable interest entities' liabilities without recourse, at fair value	1,061,497	1,337,214
Other liabilities	290,756	309,862
Total liabilities	13,373,095	16,108,465
Commitments and contingencies (See Note 14)
Common stock ($0.01 par value, 500,000,000 shares authorized; 182,235,798 and 183,744,655 shares issued and outstanding in 2011 and 2010)	1,822	1,837
Additional paid-in capital	2,569,922	2,585,423
Retained earnings	1,774,793	1,032,445
Accumulated other comprehensive income, net of tax provision of $135,344 and $18,341	367,499	111,749
Deferred equity compensation (320,193 and 181,818 shares in 2011 and 2010)	4,400	2,000
Total shareholders' equity	4,718,436	3,733,454
Total liabilities and shareholders' equity	$ 18,091,531	$ 19,841,919