Loss Reserves - Delinquent Items (Details) - loan	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Aging of the Primary Delinquent Inventory [Abstract]
3 months or less (in loans)	9,194	11,542	7,567
3 months or less (as a percent)	17.00%	20.00%	28.00%
4 - 11 months (in loans)	29,832	34,620	9,535
4 - 11 months (as a percent)	57.00%	60.00%	35.00%
12 months or more (in loans)	13,749	11,548	10,282
12 months or more (as a percent)	26.00%	20.00%	37.00%
Total primary delinquent inventory (in loans)	52,775	57,710	27,384	30,028
Total primary delinquent inventory (as a percent)	100.00%	100.00%	100.00%
Primary claims received inventory included in ending delinquent inventory (in loans)	151	159	472
Percent of 12 months or more delinquent inventory, delinquent for more than 36 months (as a percent)	26.00%	31.00%	34.00%