Loss Reserves - Reconciliation of Beginning and Ending Balances (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Loss Reserve [Roll Forward]
Reserve at beginning of period	$ 880,537	$ 555,334
Less reinsurance recoverable	95,042	21,641
Net reserve at beginning of period	785,495	533,693
Losses and LAE incurred in respect of delinquency notices received in:
Current year	67,068	265,546
Prior years	1,732	12,784
Total losses incurred	68,800	278,330
Losses and LAE paid in respect of delinquency notices received in:
Current year	48	271
Prior years	29,164	77,820
Reinsurance terminations	0	(20)
Total losses paid	29,212	78,071
Net reserve at end of period	825,083	733,952
Plus reinsurance recoverables	111,153	63,444
Reserve at end of period	$ 936,236	$ 797,396