Loss Reserves (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) loan	Jun. 30, 2016 loan	Jun. 30, 2017 USD ($) loan	Jun. 30, 2016 USD ($) loan	Dec. 31, 2016 USD ($)
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Other items removed from inventory (in loans)	(1,114)	(135)	(1,128)	(1,273)
Prior years | $			$ 298,847	$ 392,007
Premium refund liability, expected claim payments | $	$ 74,000		74,000		$ 85,000
Prior years | $			$ (103,948)	$ (64,941)
Primary Default Inventory [Roll Forward]
Default inventory at the beginning of period (in loans)	45,349	55,590	50,282	62,633
New notices (in loans)	14,463	16,080	29,402	32,811
Cures (in loans)	(14,708)	(15,640)	(31,836)	(34,693)
Paids (including those charged to a deductible or captive) (in loans)	(2,573)	(3,195)	(5,208)	(6,568)
Rescissions and denials (in loans)	(100)	(142)	(195)	(352)
Other items removed from inventory (in loans)	(1,114)	(135)	(1,128)	(1,273)
Default inventory at end of period (in loans)	41,317	52,558	41,317	52,558
Decrease in estimated claim rate on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Percentage of prior year default inventory resolved (as a percent)			48.00%	43.00%
Prior years | $			$ (104,000)	$ (76,000)
Increase in estimated severity on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $			2,000	17,000
Change in estimates related to pool reserves, LAE reserves and reinsurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $			(2,000)	(6,000)
Settlements for claims paying practices and nonperforming loan sale
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years | $			$ 45,000	$ 51,000