Schedule II Financial Information of Registrant Parent Company Only Financial Information (Details) (USD $)	12 Months Ended										3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2010 Seven Point Seven Five Percent Debentures due 2011 [Member]	Dec. 31, 2009 Seven Point Seven Five Percent Debentures due 2011 [Member]	Dec. 31, 2011 Seven Point Seven Five Percent Debentures due 2011 [Member]	May 01, 2001 Seven Point Seven Five Percent Debentures due 2011 [Member]	Dec. 31, 2011 3.00% Convertible Senior Notes due 2017 [Member]	Dec. 31, 2010 3.00% Convertible Senior Notes due 2017 [Member]	Nov. 01, 2010 3.00% Convertible Senior Notes due 2017 [Member]	Dec. 31, 2009 Parent Company	Dec. 31, 2011 Parent Company	Dec. 31, 2010 Parent Company		Dec. 31, 2009 Parent Company	Dec. 31, 2010 Parent Company Seven Point Seven Five Percent Debentures due 2011 [Member]	Dec. 31, 2011 Radian Guaranty Inc [Member]	Dec. 31, 2010 Radian Guaranty Inc [Member]	Dec. 31, 2010 CMAC Of Texas [Member]
Balance Sheet Related Disclosures
Trading Securities	$ 4,211,059,000	$ 4,562,821,000										$ 387,239,000	$ 482,873,000
Short-term Investments	1,261,703,000	1,537,498,000										177,116,000	333,687,000
Other Investments and Securities, at Cost	61,000,000	59,627,000										25,000,000	25,000,000
Cash	35,589,000	20,334,000	41,574,000								325,000	453,000	1,945,000		325,000
Restricted Cash and Cash Equivalents	27,020,000	31,413,000										1,060,000	1,835,000
Investments In Subsidiaries At Equity In Net Assets												1,591,914,000	1,027,499,000	[1]
Unamortized Debt Issuance Expense												8,414,000	9,804,000
Related Party Transaction, Due from (to) Related Party												(2,451,000)	(7,306,000)				100,000,000
Property, Plant and Equipment, Net	11,044,000	13,024,000										2,017,000	3,755,000
Other Assets	333,566,000	323,320,000										35,474,000	20,886,000
Total assets	6,656,765,000	7,620,887,000	8,057,158,000									2,231,138,000	1,914,590,000
Accounts Payable and Other Accrued Liabilities												123,665,000	31,734,000
Interest Payable												7,558,000	8,594,000
Long-term Debt	818,584,000	964,788,000		160,344,000		0		316,498,000	300,367,000			818,584,000	964,788,000
Accrued Income Taxes												99,040,000	49,644,000	[1]
Total liabilities	5,474,474,000	6,761,107,000										1,048,847,000	1,054,760,000
Common Stock, Value, Issued	151,000	150,000										151,000	150,000
Treasury Stock, Value	(892,052,000)	(892,012,000)										(892,052,000)	(892,012,000)
Additional paid-in capital	1,966,565,000	1,963,092,000										1,966,565,000	1,963,092,000
Retained Earnings (Accumulated Deficit)	96,227,000	(204,926,000)										96,227,000	(204,926,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	11,400,000	(6,524,000)										11,400,000	(6,524,000)
Total stockholders’ equity	1,182,291,000	859,780,000										1,182,291,000	859,780,000
Total Liabilities And Stockholders Equity Parent Company												2,231,138,000	1,914,540,000
Income Statement [Abstract]
Net Investment Income												15,890,000	8,626,000		222,000
Net gains on investments	(202,177,000)	(139,944,000)	(257,141,000)									(24,603,000)	(61,120,000)		(280,000)
Net gains (losses) on other financial instruments	193,329,000	(211,681,000)	(88,569,000)									1,085,000	2,496,000		11,970,000
Other Income	5,599,000	8,696,000	14,026,000									3,000	220,000		280,000
Total revenues	1,947,843,000	417,465,000	1,313,378,000									41,581,000	72,462,000		12,752,000
Interest expense	61,394,000	41,777,000	46,010,000									16,132,000	1,911,000		0
Total expenses	61,394,000	41,777,000	46,010,000									16,132,000	1,911,000		0
Pretax income (loss)	368,512,000	(1,579,678,000)	(242,280,000)									25,449,000	70,551,000		12,752,000
Income Tax Expense (Benefit)	66,362,000	226,189,000	(94,401,000)									(201,741,000)	(209,235,000)	[1]	7,563,000
Equity In Net Income (Loss) Of Affiliate												74,960,000	(2,085,653,000)	[1]	(153,068,000)
Net income (loss)	302,150,000	(1,805,867,000)	(147,879,000)									302,150,000	(1,805,867,000)		(147,879,000)
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income (loss)	302,150,000	(1,805,867,000)	(147,879,000)									302,150,000	(1,805,867,000)		(147,879,000)
Net gains on investments	(202,177,000)	(139,944,000)	(257,141,000)									(24,603,000)	(61,120,000)		(280,000)
Gains (Losses) on Extinguishment of Debt				2,500,000	12,000,000							0	(2,496,000)		(11,970,000)
Equity in undistributed net (income) loss of subsidiaries and affiliates												(400,561,000)	2,049,175,000	[1]	258,483,000
Increase (decrease) in federal income taxes												49,396,000	(274,778,000)	[1]	11,968,000
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries												0	0		74,369,000
Change in other assets	65,388,000	(34,405,000)	3,641,000									13,384,000	35,797,000		6,041,000
Change in accounts payable and accrued expenses	53,836,000	(20,014,000)	30,342,000									90,895,000	(20,711,000)		8,403,000
Net Cash Provided by (Used in) Operating Activities												30,661,000	(80,000,000)		199,135,000
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from sales of fixed-maturity investments available for sale	136,217,000	1,218,460,000	2,463,626,000									0	4,083,000		3,924,000
Sales/redemptions of trading securities	6,028,267,000	4,735,215,000	536,601,000									151,840,000	57,989,000		0
Purchases of trading securities	(5,456,565,000)	(6,126,303,000)	(2,577,599,000)									32,825,000	455,724,000		0
Sales/redemptions of short-term investments, net	276,082,000	(86,071,000)	(271,041,000)									156,665,000	(230,392,000)		(51,159,000)
Purchases of other invested assets												0	(25,000,000)		0
Purchases of property and equipment, net	2,976,000	2,516,000	4,300,000									(523,000)	(1,367,000)		(2,390,000)
Capital contributions to subsidiaries and affiliates												(145,987,000)	(423,146,000)		(5,600,000)
Capital distributions (to) from subsidiaries and affiliates												7,000	268,530,000		0
Net cash provided by (used in) investing activities	1,072,655,000	(47,785,000)	83,461,000									129,177,000	(805,027,000)		(55,225,000)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payments of Dividends, Common Stock	1,330,000	1,202,000	827,000									(1,330,000)	(1,202,000)		(827,000)
Issuance of long-term debt												0	391,310,000		0
Repayments of Lines of Credit	0	0	100,000,000												(100,000,000)
Paydown of other borrowings												0	0
Extinguishment of Debt, Amount	160,000,000	29,348,000	45,622,000									(160,000,000)	(29,348,000)		(45,622,000)
Proceeds from Issuance of Common Stock	0	525,887,000	0									0	525,887,000		0
Net Cash Provided by (Used in) Financing Activities	(161,326,000)	886,647,000	(146,449,000)									(161,330,000)	886,647,000		(146,449,000)
Cash and Cash Equivalents, Period Increase (Decrease)	15,255,000	(21,240,000)	(34,255,000)									(1,492,000)	1,620,000		(2,539,000)
Cash, beginning of period	20,334,000	41,574,000	75,829,000									1,945,000	325,000		2,864,000
Cash, end of period	35,589,000	20,334,000	41,574,000								325,000	453,000	1,945,000		325,000
Supplemental Notes [Abstract]
Prior Period Adjustment, Provision For Income Taxes													79,700,000
Restricted Funds Included In Short Term Investments												27,700,000	19,400,000
Restricted Cash Held As Collateral For Insurance Trust Agreement												1,100,000	900,000
Costs and Expenses	1,579,396,000	2,011,811,000	1,588,884,000									100,700,000	105,200,000		115,800,000
Distributions from subsidiaries and affiliates												0	0		74,369,000
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Sale of Interest by Parent											98,000,000
Capital Contributions												146,000,000						322,000,000	101,000,000
Redemption of long-term debt				31,900,000	57,700,000											31,900,000
Debt Instrument, Interest Rate, Stated Percentage						7.75%	7.75%	3.00%		3.00%
Debt Instrument, Face Amount							250,000,000	450,000,000	450,000,000	450,000,000
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months												0
Long-term Debt, Maturities, Repayments of Principal in Year Two												252,267,000
Long-term Debt, Maturities, Repayments of Principal in Year Three												0
Long-term Debt, Maturities, Repayments of Principal in Year Four												249,819,000
Long-term Debt, Maturities, Repayments of Principal in Year Five												0
Long-term Debt, Maturities, Repayments of Principal after Year Five												316,498,000
Long-term Debt	818,584,000	964,788,000		160,344,000		0		316,498,000	300,367,000			818,584,000	964,788,000
Subsidiary or Equity Method Investee, Cumulative Proceeds Received on All Transactions												17,000,000
Payments for (Proceeds from) Businesses and Interest in Affiliates																	6,000,000
Related Party Transaction, Due from (to) Related Party												$ (2,451,000)	$ (7,306,000)				$ 100,000,000

[1] See Note A