Loss Reserves (Details) (USD $)	3 Months Ended				9 Months Ended				12 Months Ended				36 Months Ended
	Sep. 30, 2013 Loan		Sep. 30, 2012 Loan		Sep. 30, 2013 Loan		Sep. 30, 2012 Loan		Dec. 31, 2012 Loan		Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Loan
Loss Reserve [Roll Forward]
Reserve at beginning of period					$ 4,056,843,000		$ 4,557,512,000		$ 4,557,512,000
Less reinsurance recoverable					104,848,000		154,607,000		154,607,000
Net reserve at end of period	3,282,373,000	[1]	3,886,142,000	[1]	3,282,373,000	[1]	3,886,142,000	[1]	3,951,995,000	[2]			4,402,905,000	[2]
Losses and LAE incurred in respect of default notices related to:
Current year					686,454,000		1,091,326,000
Prior years					(43,783,000)	[3]	287,291,000	[3]
Subtotal					642,671,000	[4]	1,378,617,000	[4]
Losses and LAE paid in respect of default notices related to:
Current year					28,792,000		54,813,000
Prior years					1,286,833,000		1,840,992,000
Reinsurance terminations					(3,332,000)	[5]	(425,000)	[5]
Subtotal					1,312,293,000	[6]	1,895,380,000	[6]
Net reserve at end of period	3,282,373,000	[1]	3,886,142,000	[1]	3,282,373,000	[1]	3,886,142,000	[1]	3,951,995,000	[2]			4,402,905,000	[2]
Plus reinsurance recoverables	70,621,000		117,859,000		70,621,000		117,859,000		104,848,000				154,607,000
Reserve at end of period	3,352,994,000		4,004,001,000		3,352,994,000		4,004,001,000		4,056,843,000				4,557,512,000
Loss reserve reduction from rescission	100,000,000		500,000,000		100,000,000		500,000,000		200,000,000				700,000,000
Paid losses mitigated by rescission amount					100,000,000		200,000,000
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves					(44,000,000)	[7]	287,000,000	[7]
Historical average period for uncured default to develop into paid claim					12 months
Premium refund liability, expected claim payments	145,000,000				145,000,000				134,000,000
Primary Default Inventory [Roll Forward]
Default inventory at the beginning of period	117,105		153,990		139,845		175,639		175,639
New Notices	27,755		34,432		81,044		101,454
Cures	(24,105)		(27,384)		(80,677)		(90,896)
Paids (including those charged to a deductible or captive)	(8,659)		(11,344)		(27,155)		(34,991)
Rescissions and denials	(509)		(809)		(1,470)		(2,321)
Default inventory at end of period	111,587		148,885		111,587		148,885		139,845				175,639
Loss Contingencies [Line Items]
Number of rescindable loans affected by Company's decision to suspend rescissions for customers settlement agreement probable	540				540
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for customers settlement agreements probable	38,000,000				38,000,000
Number of rescindable loans affected by Company's decision to suspend rescissions for all other customers	85				85
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for all other customers	5,000,000				5,000,000
Pool insurance notice inventory [Abstract]
Pool insurance notice inventory (in number of loans)	6,821		9,337		6,821		9,337		8,594
Aging of the Primary Default Inventory [Abstract]
3 months or less	20,144		25,593		20,144		25,593		23,282
3 months or less (in hundredths)	18.00%		17.00%		18.00%		17.00%		17.00%
4 - 11 months	24,138		35,029		24,138		35,029		34,688
4 - 11 months (in hundredths)	22.00%		24.00%		22.00%		24.00%		25.00%
12 months or more	67,305		88,263		67,305		88,263		81,875
12 months or more (in hundredths)	60.00%		59.00%		60.00%		59.00%		58.00%
Total primary default inventory	111,587		148,885		111,587		148,885		139,845				175,639
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	9,858	[8]	12,508	[8]	9,858	[8]	12,508	[8]	11,731	[8]
Primary claims received inventory included in ending default inventory (in hundredths)	9.00%	[8]	8.00%	[8]	9.00%	[8]	8.00%	[8]	8.00%	[8]
Number of payments delinquent [Abstract]
3 payments or less	28,777		35,130		28,777		35,130		34,245
3 payments or less (in hundredths)	26.00%		24.00%		26.00%		24.00%		24.00%
4 - 11 payments	25,089		36,359		25,089		36,359		34,458
4 - 11 payments (in hundredths)	22.00%		24.00%		22.00%		24.00%		25.00%
12 payments or more	57,721		77,396		57,721		77,396		71,142
12 payments or more (in hundredths)	52.00%		52.00%		52.00%		52.00%		51.00%
Total primary default inventory	111,587		148,885		111,587		148,885		139,845				175,639
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					100,000,000				300,000,000				3,000,000,000
Percentage of claims received in a quarter resolved by rescission, lower range limit (in hundredths)					5.00%
Percentage of claims received in a quarter resolved by rescission, upper range limit (in hundredths)					28.00%
Estimated Rescission Reduction - Loss Reserve [Roll Forward]
Estimated rescission reduction - losses incurred									(200,000,000)		200,000,000	2,500,000,000
Estimated rescission reduction - ending reserve	100,000,000				100,000,000				200,000,000
Rescissions dispute period not ended (in hundredths)	32.00%				32.00%
Premium refund liability, expected future rescissions	15,000,000				15,000,000				18,000,000
Statute of limitations to bring legal proceedings disputing right to rescind coverage					3 years
Countrywide Home Loans [Member] | Pending Litigation [Member]
Loss Contingencies [Line Items]
Number of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	800				800
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	70,000,000				70,000,000
Bank of America NA [Member] | Pending Litigation [Member]
Loss Contingencies [Line Items]
Number of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	2,100				2,100
Total potential claim payments of rescindable loans affected by Company's decision to suspend rescissions for Countrywide	150,000,000				150,000,000
Increase (Decrease) in Estimated Claim Rate On primary Defaults [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves					10,000,000	[7]	300,000,000	[7]
Percentage of prior year default inventory resolved (in hundredths)					48.00%		46.00%
Increase (Decrease) in Estimated Severity, Primary Defaults [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves					(40,000,000)	[7]	0	[7]
Change In Estimates 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					$ (14,000,000)	[7]	$ (13,000,000)	[7]

[1] At September 30, 2013 and 2012, the estimated reduction in loss reserves related to rescissions approximated $0.1 billion and $0.5 billion, respectively.

[2] At December 31, 2012 and 2011, the estimated reduction in loss reserves related to rescissions approximated $0.2 billion and $0.7 billion, respectively.

[3] 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.

[4] Rescissions did not have a significant impact on incurred losses in the nine months ended September 30, 2013 or 2012.

[5] 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.

[6] Rescissions mitigated our paid losses by an estimated $0.1 billion and $0.2 billion in the nine months ended September 30, 2013 and 2012, respectively, which excludes amounts that may have been applied to a deductible.

[7] A negative number for prior year loss development indicates a redundancy of prior year loss reserves, and a positive number indicates a deficiency of prior year loss reserves.

[8] Our claims received inventory includes suspended rescission as discussed in Note 5 – “Litigation and Contingencies.” In connection with the Countrywide proceedings, we have voluntarily suspended rescissions of coverage related to loans that we believed would be included in a potential resolution. As of September 30, 2013, coverage on approximately 2,100 loans under the agreement with BANA, representing total potential claim payments of approximately $150 million and 800 loans under the agreement with CHL, representing total potential claims payments of approximately $70 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. As of September 30, 2013, coverage on approximately 540 loans, representing total potential claim payments of approximately $38 million, was affected by our decision to suspend rescissions for other customers for which we also consider settlement probable. In addition, as of September 30, 2013, coverage on approximately 85 loans, representing total potential claim payments of approximately $5 million, was affected by our decision to suspend rescissions for customers other than those for which we consider settlement probable, as defined in ASC 450-20.