Loss Reserves - Delinquent Items (Details) - loan	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Aging of the Primary Delinquent Inventory [Abstract]
3 months or less (in loans)	8,970		9,829	8,554
3 months or less (as a percent)	30.00%		30.00%	24.00%
4 - 11 months (in loans)	8,951		9,655	12,506
4 - 11 months (as a percent)	30.00%		29.00%	35.00%
12 months or more (in loans)	11,874		13,414	14,977
12 months or more (as a percent)	40.00%		41.00%	41.00%
Total primary delinquent inventory (in loans)	29,795	30,921	32,898	36,037	41,243	46,556
Total primary delinquent inventory (as a percent)	100.00%		100.00%	100.00%
Primary claims received inventory included in ending delinquent inventory (in loans)	630		809	827
Percent of 12 months or more delinquent inventory, delinquent for more than 36 months (as a percent)	37.00%		38.00%	43.00%