Loss Reserves, Change in Liability and Claims Adjustment Expense (Details) (USD $)	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2014 Loan		Sep. 30, 2013 Loan		Sep. 30, 2014 Loan		Sep. 30, 2013 Loan		Dec. 31, 2012 Loan	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2013 Loan
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves					$ (75,387,000)	[1],[2]	$ (43,783,000)	[1],[2]
Historical average period for uncured default to develop into paid claim					12 months
Premium refund liability, expected claim payments	112,000,000				112,000,000							131,000,000
Primary Default Inventory [Roll Forward]
Default inventory at the beginning of period	85,416		117,105		103,328		139,845
New Notices	22,927		27,755		67,451		81,044
Cures	(19,582)		(24,105)		(68,082)		(80,677)
Paids (including those charged to a deductible or captive)	(5,288)		(8,659)		(18,420)		(27,155)
Rescissions and denials	(319)		(509)		(1,123)		(1,470)
Default inventory at end of period	83,154		111,587		83,154		111,587		139,845
Pool insurance notice inventory [Abstract]
Pool insurance notice inventory (in number of loans)	4,525		6,821		4,525		6,821					6,563
Aging of the Primary Default Inventory [Abstract]
3 months or less	16,209		20,144		16,209		20,144					18,941
3 months or less (in hundredths)	19.00%		18.00%		19.00%		18.00%					18.00%
4 - 11 months	18,890		24,138		18,890		24,138					24,514
4 - 11 months (in hundredths)	23.00%		22.00%		23.00%		22.00%					24.00%
12 months or more	48,055		67,305		48,055		67,305					59,873
12 months or more (in hundredths)	58.00%		60.00%		58.00%		60.00%					58.00%
Total primary default inventory	83,154		111,587		83,154		111,587		139,845
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	5,194	[3]	9,858	[3]	5,194	[3]	9,858	[3]				6,948	[3]
Primary claims received inventory included in ending default inventory (in hundredths)	6.00%	[3]	9.00%	[3]	6.00%	[3]	9.00%	[3]				7.00%	[3]
Number of rescindable loans affected by Company's decision to voluntarily suspend rescissions	1,575				1,575
Number of payments delinquent [Abstract]
3 payments or less	23,769		28,777		23,769		28,777					28,095
3 payments or less (in hundredths)	28.00%		26.00%		28.00%		26.00%					27.00%
4 - 11 payments	18,985		25,089		18,985		25,089					24,605
4 - 11 payments (in hundredths)	23.00%		22.00%		23.00%		22.00%					24.00%
12 payments or more	40,400		57,721		40,400		57,721					50,628
12 payments or more (in hundredths)	49.00%		52.00%		49.00%		52.00%					49.00%
Total primary default inventory	83,154		111,587		83,154		111,587		139,845
Total primary default inventory (in hundredths)	100.00%		100.00%		100.00%		100.00%					100.00%
Estimated Rescission Reduction - Loss Reserve [Roll Forward]
Estimated rescission reduction - losses incurred									(200,000,000)	200,000,000	2,500,000,000
Premium refund liability, expected future rescissions	29,000,000				29,000,000							15,000,000
(Decrease) increase 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					(38,000,000)	[1]	10,000,000	[1]
Percentage of prior year default inventory resolved (in hundredths)					50.00%		48.00%
Decrease in estimated severity on primary defaults [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves					(20,000,000)	[1]	(40,000,000)	[1]
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					$ (17,000,000)	[1]	$ (14,000,000)	[1]

[1] 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.

[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] Our claims received inventory includes suspended rescissions, as we have voluntarily suspended rescissions of coverage related to certain loans that we believed would be included in a potential resolution. As of September 30, 2014, rescissions of coverage on approximately 1,575 loans had been voluntarily suspended.