Loss Reserves - Aging of Primary Default Inventory (Details) - loan	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Aging of the Primary Default Inventory [Abstract]
3 months or less	8,820	7,586	11,542
4 - 11 months	8,217	7,990	34,620
12 months or more	9,350	17,714	11,548
Total primary default inventory	26,387	33,290	57,710	30,028
3 months of less (in hundreds, as a percent)	33.00%	23.00%	20.00%
4 - 11 months (in hundredths, as a percent)	31.00%	24.00%	60.00%
12 months or more (in hundredths, as a percent)	36.00%	53.00%	20.00%
Total primary default inventory (in hundredths, as a percent)	100.00%	100.00%	100.00%
Primary claims received inventory included in ending delinquent inventory	267	211	159
Percent of inventory in default for more than 36 consecutive months (as a percent)	36.00%	20.00%	31.00%