Reinsurance - Schedule of Ceded Premiums Earned by Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Effects of Reinsurance [Line Items]
Ceded Premiums Written	$ (36,471)	$ (7,841)	$ (422,367)	$ (204,004)
Increase (Decrease) in Ceded Unearned Premiums	(79,036)	(45,458)	130,012	55,167
Ceded Premiums Earned	(115,507)	(53,299)	(292,355)	(148,837)
Excess of Loss Product Line
Effects of Reinsurance [Line Items]
Ceded Premiums Written	(28,306)	(476)	(400,773)	(182,503)
Equipment and Identity Theft Product Line
Effects of Reinsurance [Line Items]
Ceded Premiums Written	(2,606)	(2,359)	(7,275)	(6,136)
Flood Product Line
Effects of Reinsurance [Line Items]
Ceded Premiums Written	(5,559)	(5,006)	(14,319)	(12,969)
Novation of Auto Policies [Member]
Effects of Reinsurance [Line Items]
Ceded Premiums Written	$ 0	$ 0	$ 0	$ (2,396)