Loss Reserves - Reconciliation of Beginning and Ending Balances (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Loss Reserve [Roll Forward]
Reserve at beginning of period	$ 555,334	$ 674,019
Less reinsurance recoverable	21,641	33,328
Net reserve at beginning of period	533,693	640,691
Losses and LAE incurred in respect of delinquency notices received in:
Current year	301,699	142,644
Prior years	17,317	(47,760)
Total losses incurred	319,016	94,884
Losses and LAE paid in respect of delinquency notices received in:
Current year	1,486	980
Prior years	93,937	165,844
Reinsurance terminations	(20)	(13,980)
Total losses paid	95,403	152,844
Net reserve at end of period	757,306	582,731
Plus reinsurance recoverables	83,143	19,566
Reserve at end of period	$ 840,449	$ 602,297