Loss Reserves - Prior Year Loss Reserves (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior years	[1],[2]	$ (110,302)	$ (100,359)	$ (59,687)
(Decrease) Increase in Estimated Claim Rate on primary Defaults
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior years		(141,000)	(43,000)	10,000
Increase (Decrease) in Estimated Severity, Primary Defaults
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior years		43,000	(35,000)	(50,000)
Change in Estimates Related to Pool Reserves, LAE Reserves, Reinsurance and Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior years		$ (12,000)	$ (22,000)	$ (20,000)

[1] A negative number for prior year loss development indicates a redundancy of prior year loss reserves.

[2] A negative number for prior year losses incurred indicates a redundancy of prior year loss reserves. See table below regarding prior year loss development.