Loss Reserves (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) loan	Sep. 30, 2020 loan	Sep. 30, 2021 USD ($) loan	Sep. 30, 2020 USD ($) loan	Dec. 31, 2020 USD ($)
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Increase (decrease) in loss reserves			$ 52,372	$ 285,115
Prior years			(5,968)	17,317
Prior years			$ 48,842	$ 93,937
Other items removed from default inventory | loan	360	0	360	0
Premium refund liability, expected claim payments	$ 37,300		$ 37,300		$ 30,100
Primary Delinquent Inventory [Roll Forward]
Delinquent inventory at the beginning of period (in loans) | loan	42,999	69,326	57,710	30,028
New notices (in loans) | loan	9,862	20,924	31,909	90,906
Cures (in loans) | loan	(14,813)	(25,446)	(50,901)	(54,523)
Paids (including those charged to a deductible or captive) (in loans) | loan	(298)	(375)	(956)	(1,933)
Rescissions and denials (in loans) | loan	(11)	(11)	(23)	(60)
Other items removed from inventory (in loans) | loan	(360)	0	(360)	0
Delinquent inventory at end of period (in loans) | loan	37,379	64,418	37,379	64,418
$1,000 Increase/Decrease In Average Severity Reserve Factor
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Increase (decrease) in loss reserves			$ 17,000
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]
Increase (decrease) in loss reserves			22,000
Change in estimates related to IBNR reserves
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Increase (decrease) in loss reserves			(5,900)	$ 12,600
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
Increase (decrease) in estimated claim rate on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			(18,147)	(1,626)
Increase (decrease) in estimated severity on primary defaults
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			(105)	13,503
Change in estimates related to pool reserves, LAE reserves, reinsurance, and other
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years			12,284	$ 5,440
Settlements for commutations of coverage of pools of nonperforming loans
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years	$ 6,700		$ 6,700