Loss Reserves (Details) (USD $)	3 Months Ended				6 Months Ended	9 Months Ended				12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Jun. 30, 2009	Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Loss Reserve [Roll Forward]
Reserve at beginning of period						$ 4,557,512,000		$ 5,884,171,000		$ 5,884,171,000
Less reinsurance recoverable						154,607,000		275,290,000		275,290,000
Net reserve at beginning of year						4,402,905,000	[1]	5,608,881,000	[1]	5,608,881,000	[1]
Loss Reserve Reduction From Rescission	500,000,000		800,000,000			500,000,000		800,000,000		700,000,000		1,300,000,000
Losses and LAE incurred in respect of default notices received to [Abstract]
Current year						1,091,326,000		1,328,906,000
Prior years						287,291,000	[2]	(96,269,000)	[2]
Subtotal						1,378,617,000	[3]	1,232,637,000	[3]
Losses and LAE paid in respect of default notices received to [Abstract]
Current year						54,813,000		37,111,000
Prior years						1,840,992,000		2,218,490,000
Reinsurance terminations						(425,000)	[4]	(38,769,000)	[4]
Subtotal						1,895,380,000	[5]	2,216,832,000	[5]
Net reserve at end of period	3,886,142,000	[6]	4,624,686,000	[6]		3,886,142,000	[6]	4,624,686,000	[6]	4,402,905,000	[1]	5,608,881,000	[1]
Plus reinsurance recoverables	117,859,000		166,874,000			117,859,000		166,874,000		154,607,000		275,290,000
Reserve at end of period	4,004,001,000		4,791,560,000			4,004,001,000		4,791,560,000		4,557,512,000		5,884,171,000
Paid Losses Mitigated By Rescission Amount						200,000,000		500,000,000
Loss Reserve Reduction From Rescission	500,000,000		800,000,000			500,000,000		800,000,000		700,000,000		1,300,000,000
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Historical average period for uncured default to develop into paid claim						12 months
Premium refund liability, expected claim payments	118,000,000					118,000,000				114,000,000
Aging of the Primary Default Inventory [Abstract]
3 months or less	25,593		33,167			25,593		33,167		31,456
3 months or less (in hundredths)	17.00%		18.00%			17.00%		18.00%		18.00%
4 - 11 months	35,029		45,110			35,029		45,110		46,352
4 - 11 months (in hundredths)	24.00%		25.00%			24.00%		25.00%		26.00%
12 months or more	88,263		102,617			88,263		102,617		97,831
12 months or more (in hundredths)	59.00%		57.00%			59.00%		57.00%		56.00%
Total primary default inventory	148,885		180,894			148,885		180,894		175,639		214,724
Total primary default inventory (in hundredths)	100.00%		100.00%			100.00%		100.00%		100.00%
Primary claims received inventory included in ending default inventory	12,508	[7]	13,799	[7]		12,508	[7]	13,799	[7]	12,610	[7]
Primary claims received inventory included in ending default inventory (in hundredths)	8.00%	[7]	8.00%	[7]		8.00%	[7]	8.00%	[7]	7.00%	[7]
Number of rescindable loans affected by Company's decision to suspend rescissions	1,700					1,700
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions	125,000,000					125,000,000
Number of rescindable loans affected by Company's decision to suspend rescissions for customers other than Countrywide	350					350
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for customers other than Countrywide	23,000,000					23,000,000
Number of payments delinquent [Abstract]
3 payments or less	35,130		43,312			35,130		43,312		42,804
3 payments or less (in hundredths)	24.00%		24.00%			24.00%		24.00%		24.00%
4 - 11 payments	36,359		47,929			36,359		47,929		47,864
4 - 11 payments (in hundredths)	24.00%		26.00%			24.00%		26.00%		27.00%
12 payments or more	77,396		89,653			77,396		89,653		84,971
12 payments or more (in hundredths)	52.00%		50.00%			52.00%		50.00%		49.00%
Total primary default inventory	148,885		180,894			148,885		180,894		175,639		214,724
Total primary default inventory (in hundredths)	100.00%		100.00%			100.00%		100.00%		100.00%
Claims resolved by rescissions [Abstract]
Mitigation of paid losses by rescission of policies						200,000,000				600,000,000		1,200,000,000		1,200,000,000
Percentage of claims received in a quarter resolved by rescission, lower range limit (in hundredths)						8.00%								8.00%
Percentage of claims received in a quarter resolved by rescission, upper range limit (in hundredths)					28.00%	13.00%								13.00%
Number of rescindable loans affected by Company's decision to suspend rescissions	1,700					1,700
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions	125,000,000					125,000,000
Number of rescindable loans affected by Company's decision to suspend rescissions for customers other than Countrywide	350					350
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for customers other than Countrywide	23,000,000					23,000,000
Estimated Rescission Reduction - Loss Reserve [Roll Forward]
Estimated rescission reduction - beginning reserve	600,000,000		900,000,000			700,000,000		1,300,000,000		1,300,000,000
Estimated rescission reduction - losses incurred	0		0			0		0
Rescission reduction - paid claims	100,000,000		100,000,000			200,000,000		500,000,000
Amounts that may have been applied to a deductible	0		0			0		0
Net rescission reduction - paid claims	100,000,000		100,000,000			200,000,000		500,000,000
Estimated rescission reduction - ending reserve	500,000,000	[8]	800,000,000	[8]		500,000,000	[8]	800,000,000	[8]	700,000,000		1,300,000,000
Premium refund liability, expected future rescissions	49,000,000					49,000,000				58,000,000
Statute of limitations to bring legal proceedings disputing right to rescind coverage	3 years					3 years
Number of settlement agreements approved by GSEs	1					1
Primary Default Inventory [Roll Forward]
Default inventory at beginning of period	153,990		184,452			175,639		214,724		214,724
Plus: New Notices	34,432		44,342			101,454		127,509
Less: Cures	(27,384)		(34,335)			(90,896)		(115,806)
Less: Paids (including those charged to a deductible or captive)	(11,344)		(12,033)			(34,991)		(39,052)
Less: Rescissions and denials	(809)		(1,532)			(2,321)		(6,481)
Default inventory at end of period	148,885		180,894			148,885		180,894		175,639		214,724
Pool insurance notice inventory [Abstract]
Pool insurance notice inventory (in number of loans)	9,337		33,792			9,337		33,792		32,971
Number of notices removed from pool notice inventory	15,600
Increase (Decrease) in Severity, Primary Defaults [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves								105,000,000
Percentage of prior year default inventory resolved (in hundredths)								49.00%
Decrease in Estimated Loss Adjustment Expenses [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves								121,000,000
Increase (Decrease) in Expected Claim Rate [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves						300,000,000		180,000,000
Increase (Decrease) in Severity, Pool Defaults [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves								50,000,000
Increase (Decrease) Related to Pool Reserves, LAE Reserves and Reinsurance [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves						$ 13,000,000

[1] At December 31, 2011 and 2010, the estimated reduction in loss reserves related to rescissions approximated $0.7 billion and $1.3 billion, respectively.

[2] A negative number for prior year losses incurred indicates a redundancy of prior year loss reserves, and a positive number for prior year losses incurred indicates a deficiency of prior year loss reserves.

[3] Rescissions did not have a significant impact on incurred losses in the nine months ended September 30, 2012 or 2011.

[4] In a termination, the reinsurance agreement is cancelled, with no future premium ceded and funds for any incurred but unpaid losses transferred to us. The transferred funds result in an increase in our investment portfolio (including cash and cash equivalents) and a decrease in net losses paid (reduction to losses incurred). In addition, there is an offsetting decrease in the reinsurance recoverable (increase in losses incurred), and thus there is no net impact to losses incurred.

[5] Rescissions mitigated our paid losses by an estimated $0.2 billion in the nine months ended September 30, 2012 and by an estimated $0.5 billion in the nine months ended September 30, 2011, which excludes amounts that may have been applied to a deductible.

[6] At September 30, 2012 and 2011, the estimated reduction in loss reserves related to rescissions approximated $0.5 billion and $0.8 billion, respectively.

[7] As discussed in Note 5 – "Litigation and Contingencies" we are in mediation in an effort to resolve our dispute with Countrywide. In connection with that mediation, we have voluntarily suspended rescissions of coverage related to loans that we believe could be included in a potential resolution. As of September 30, 2012, coverage on approximately 1,700 loans, representing total potential claim payments of approximately $125 million, that we had determined was rescindable was affected by our decision to suspend such rescissions. Substantially all of these potential rescissions relate to claims received beginning in the first quarter of 2011 or later and, had we not suspended rescissions, most of these rescissions would have been processed in the first nine months of 2012. In addition, as of September 30, 2012, approximately 350 rescissions, representing total potential claim payments of approximately $23 million, were affected by our decision to suspend rescissions for customers other than Countrywide.

[8] As noted in Note 5 – "Litigation and Contingencies" we are in mediation in an effort to resolve our dispute with Countrywide. In connection with that mediation, we have voluntarily suspended rescissions of coverage related to loans that we believe could be included in a potential resolution. As of September 30, 2012, coverage on approximately 1,700 loans, representing total potential claim payments of approximately $125 million, that we had determined was rescindable was affected by our decision to suspend such rescissions. Substantially all of these potential rescissions relate to claims received beginning in the first quarter of 2011 or later and, had we not suspended rescissions, most of these rescissions would have been processed in the first nine months of 2012. In addition, as of September 30, 2012, approximately 350 rescissions, representing total potential claim payments of approximately $23 million, were affected by our decision to suspend rescissions for customers other than Countrywide. Although the loans with suspended rescissions are included in our delinquency inventory, for purposes of determining our reserve amounts, it is assumed that coverage on these loans will be rescinded, and thus are included in the estimated $0.5 million estimated rescission reduction to ending reserves at September 30, 2012. The decision to suspend these potential rescissions does not represent the only reason for the recent decline in the percentage of claims that have been resolved through rescissions and we continue to expect that our rescissions will continue to decline.