Reinsurance - Narrative (Details) - USD ($)		3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Effects of Reinsurance [Line Items]
Ceded		$ 41,096,000	$ 21,378,000	$ 71,820,000	$ 54,643,000
Quota Share Reinsurance Agreement, 2019
Effects of Reinsurance [Line Items]
Contingent termination fee				$ 0
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent)				90.00%
Quota share for all policies covered (as a percent)				30.00%
Cede rate, option 1 (as a percent)				25.00%
Cede rate, option 2 (as a percent)				20.00%
Ceding commission, percentage (as a percent)				20.00%
Loss ratio threshold for profit commissions (as a percent)				62.00%
Quota Share Reinsurance Agreement, 2015
Effects of Reinsurance [Line Items]
Contingent termination fee	$ 0	6,800,000
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent)				90.00%
Quota share for all policies covered (as a percent)	15.00%			30.00%
Loss ratio threshold for profit commissions (as a percent)	68.00%
Excess of Loss Reinsurance Agreement, Home Re
Effects of Reinsurance [Line Items]
Ceded		$ 4,500,000		$ 7,000,000.0