Loss Reserves - Reconciliation of Beginning and Ending Balances (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Loss Reserve [Roll Forward]
Reserve at beginning of period	$ 985,635	$ 1,438,813
Less reinsurance recoverable	48,474	50,493
Net reserve at beginning of period	937,161	1,388,320
Losses and LAE incurred in respect of delinquency notices received in:
Current year	108,361	158,906
Prior years	(97,966)	(103,948)
Total losses incurred	10,395	54,958
Losses and LAE paid in respect of delinquency notices received in:
Current year	263	2,125
Prior years	173,313	298,847
Reinsurance terminations	(1,984)	0
Total losses paid	171,592	300,972
Net reserve at end of period	775,964	1,142,306
Plus reinsurance recoverables	37,051	44,783
Reserve at end of period	$ 813,015	$ 1,187,089