Loss Reserves (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) loan	Mar. 31, 2020 USD ($) loan	Dec. 31, 2020 USD ($)
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior years	$ (1,789)	$ 1,157
Premium refund liability, expected claim payments	33,000		$ 30,000
Increase (decrease) in loss reserves	$ 32,573	$ 19,419
Primary Delinquent Inventory [Roll Forward]
Delinquent inventory at the beginning of period (in loans) | loan	57,710	30,028
New notices (in loans) | loan	13,011	12,398
Cures (in loans) | loan	(17,628)	(14,113)
Paids (including those charged to a deductible or captive) (in loans) | loan	(312)	(897)
Rescissions and denials (in loans) | loan	(6)	(32)
Delinquent inventory at end of period (in loans) | loan	52,775	27,384
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	$ 87	$ (705)
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	59	3,833
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	(1,935)	(1,971)
$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	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]
Increase (decrease) in loss reserves	31,000
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	$ (4,400)	$ 7,800