Loss Reserves - Default Inventory Reconciliation (Details) - loan	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Primary Default Inventory [Roll Forward]
Delinquent inventory at beginning of year	50,282	62,633	79,901
New Notices	68,268	67,434	74,315
Cures	(61,094)	(65,516)	(73,610)
Paids (including those charged to a deductible or captive)	(9,206)	(12,367)	(16,004)
Rescissions and denials	(357)	(629)	(848)
Other items removed from inventory	(1,337)	(1,273)	(1,121)
Delinquent inventory at end of year	46,556	50,282	62,633