Ceded Premiums Earned by type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Ceded Premiums Earned by type [Line Items]
Ceded Premiums Written	$ (262,340)	$ (183,808)	$ (144,404)
Increase (Decrease) in Ceded Unearned Premiums	52,442	15,551	8,559
Ceded Premiums Earned	(209,898)	(168,257)	(135,845)
Excess of Loss Product Line
Ceded Premiums Earned by type [Line Items]
Ceded Premiums Written	(235,236)	(163,106)	(125,638)
Equipment and Identity Theft Product Line
Ceded Premiums Earned by type [Line Items]
Ceded Premiums Written	(8,313)	(6,169)	(4,370)
Flood Product Line
Ceded Premiums Earned by type [Line Items]
Ceded Premiums Written	(16,395)	(14,533)	(14,396)
Novation of Auto Policies
Ceded Premiums Earned by type [Line Items]
Ceded Premiums Written	$ (2,396)	$ 0	$ 0