Loss Reserves - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) loan Payment	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Minimum number of payments past due to be in default | Payment	2
Change in loss reserves (+/-)	$ 2,985	$ 325,203	$ (118,685)
Prior years	(60,015)	19,604	$ (71,006)
Premium refund liability, expected claim payments	$ 37,000	$ 30,000
Other items removed from inventory | loan	695	0	639
Prior years	$ 68,769	$ 109,923	$ 235,551
Pool insurance notice inventory (in number of loans) | loan	498	680	653
Settlements for commutations of coverage, pools of nonperforming loans
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years	$ 13,800		$ 30,000
$1,000 Increase/Decrease In Average Severity Reserve Factor
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves (+/-)	16,000
One Percentage Point Increase/Decrease In Average Claim Rate Reserve Factor
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Change in loss reserves (+/-)	19,000
Probable Loss On Litigation Claims Paying Practices
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years	$ 6,300