Loss Reserves - Delinquent Items (Details) - loan	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Aging of the Primary Delinquent Inventory [Abstract]
3 months or less (in loans)	7,567	9,447	8,568
3 months or less (as a percent)	28.00%	32.00%	28.00%
4 - 11 months (in loans)	9,535	9,664	9,997
4 - 11 months (as a percent)	35.00%	32.00%	32.00%
12 months or more (in loans)	10,282	10,917	12,356
12 months or more (as a percent)	37.00%	36.00%	40.00%
Total primary delinquent inventory (in loans)	27,384	30,028	30,921	32,898
Total primary delinquent inventory (as a percent)	100.00%	100.00%	100.00%
Primary claims received inventory included in ending delinquent inventory (in loans)	472	538	665
Percent of 12 months or more delinquent inventory, delinquent for more than 36 months (as a percent)	34.00%	36.00%	38.00%