Loss Reserves (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) loan	Sep. 30, 2015 USD ($) loan	Sep. 30, 2016 USD ($) loan	Sep. 30, 2015 USD ($) loan	Sep. 30, 2016 USD ($) loan	Dec. 31, 2015 USD ($) loan	Sep. 30, 2015 loan
Loss Reserve [Roll Forward]
Reserve at beginning of period			$ 1,893,402	$ 2,396,807
Less reinsurance recoverable			44,487	57,841
Net reserve at beginning of period			1,848,915	2,338,966
Losses and LAE incurred in respect of defaults related to:
Current year			292,090	338,611
Prior years			(99,591)	(90,130)
Subtotal			192,499	248,481
Losses and LAE paid in respect of defaults related to:
Current year			5,942	9,227
Prior years			549,706	652,465
Reinsurance terminations			(2,854)	(15,440)
Subtotal			552,794	646,252
Net reserve at end of period	$ 1,488,620	$ 1,941,195	1,488,620	1,941,195
Plus reinsurance recoverables	46,863	38,748	46,863	38,748
Reserve at end of period	$ 1,535,483	$ 1,979,943	1,535,483	1,979,943
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			(99,591)	(90,130)
Prior years			$ 549,706	$ 652,465
Premium refund liability, expected claim payments					$ 91,000	$ 102,000
Pool insurance notice inventory [Abstract]
Historical average period for uncured default to develop into paid claim			12 months
Primary Default Inventory [Roll Forward]
Default inventory at the beginning of period | loan	52,558	66,357	62,633	79,901
New notices | loan	17,607	19,509	50,418	55,856
Cures | loan	(15,556)	(17,036)	(50,249)	(56,700)
Paids (including those charged to a deductible or captive) | loan	(3,051)	(3,958)	(9,619)	(12,671)
Rescissions and denials | loan	(125)	(230)	(477)	(623)
Other items removed from inventory | loan	0	0	(1,273)	(1,121)
Default inventory at end of period | loan	51,433	64,642	51,433	64,642
Default inventory, measurement period threshold (in months)			12 months
Aging of the Primary Default Inventory [Abstract]
3 months or less | loan					12,333	13,053	13,991
3 months or less (in hundredths)					24.00%	21.00%	22.00%
4 - 11 months | loan					12,648	15,763	14,703
4 - 11 months (in hundredths)					25.00%	25.00%	23.00%
12 months or more | loan					26,452	33,817	35,948
12 months or more (in hundredths)					51.00%	54.00%	55.00%
Total primary default inventory | loan	52,558	66,357	62,633	79,901	51,433	62,633	64,642
Total primary default inventory (in hundredths)					100.00%	100.00%	100.00%
Primary claims received inventory included in ending default inventory | loan					1,636	2,769	2,982
Primary claims received inventory included in ending default inventory (in hundredths)					3.00%	4.00%	5.00%
Percent of default inventory in default for more than 36 months					48.00%	50.00%	50.00%
Number of payments delinquent [Abstract]
3 payments or less | loan					18,374	20,360	20,637
3 payments or less (in hundredths)					36.00%	33.00%	32.00%
4 - 11 payments | loan					12,282	15,092	14,890
4 - 11 payments (in hundredths)					24.00%	24.00%	23.00%
12 payments or more | loan					20,777	27,181	29,115
12 payments or more (in hundredths)					40.00%	43.00%	45.00%
Total primary default inventory | loan	52,558	66,357	62,633	79,901	51,433	62,633	64,642
Total primary default inventory (in hundredths)					100.00%	100.00%	100.00%
Pool insurance notice inventory (in number of loans) | loan					1,979	2,739	2,950
Premium refund liability, expected future rescissions					$ 6,000	$ 7,000
Decrease in estimated claim rate on primary defaults
Losses and LAE incurred in respect of defaults related to:
Prior years			$ (108,000)	$ (95,000)
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			$ (108,000)	$ (95,000)
Percentage of prior year default inventory resolved (in hundredths)			54.00%	52.00%
Increase in estimated severity on primary defaults
Losses and LAE incurred in respect of defaults related to:
Prior years			$ 12,000	$ 12,000
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			12,000	12,000
Change in estimates related to pool reserves, LAE reserves and reinsurance
Losses and LAE incurred in respect of defaults related to:
Prior years			(4,000)	(7,000)
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			(4,000)	(7,000)
Change in estimates related to disputes on claims paying practices and IBNR
Losses and LAE incurred in respect of defaults related to:
Prior years				21,000
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years				$ 21,000
Settlements For Claims Paying Practices And Nonperforming Loan Sale
Losses and LAE paid in respect of defaults related to:
Prior years			52,000
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			$ 52,000