Loss Reserves - Aging of Primary Default Inventory (Details) - loan	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Aging of the Primary Default Inventory [Abstract]
3 months or less	9,175	8,820	7,586
4 - 11 months	8,900	8,217	7,990
12 months or more	7,575	9,350	17,714
Total primary default inventory	25,650	26,387	33,290	57,710
3 months of less (in hundreds, as a percent)	36.00%	33.00%	23.00%
4 - 11 months (in hundredths, as a percent)	35.00%	31.00%	24.00%
12 months or more (in hundredths, as a percent)	29.00%	36.00%	53.00%
Total primary default inventory (in hundredths, as a percent)	100.00%	100.00%	100.00%
Primary claims received inventory included in ending delinquent inventory	302	267	211
Percent of inventory in default for more than 36 consecutive months (as a percent)	37.00%	36.00%	20.00%