Reinsurance - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 01, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid Reinsurance Premiums		$ 132,564	$ 79,399
Policyholder Benefits and Claims Incurred, Assumed and Ceded		$ 18,412	10,282
Percentage of Flood Premiums Ceded		100.00%
Insurance Commissions and Fees, Flood Program		$ 1,056	$ 959	$ 1,078
Increase (Decrease) in Ceded Losses and LAE Incurred		$ (27,913)
Minimum
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
ISO Catastrophe Definition	$ 25,000
Catastrophe
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Coverage, Percentage Placed	100.00%
Prepaid Reinsurance Premiums	$ 191,500
Catastrophe | Maximum [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Retention Policy, Amount Retained	10,000
Catastrophe | Unaffiliated Private Reinsurers [Member] | Maximum [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Aggregate Coverage for Covered Losses Under Reinsurance Contract	$ 685,000
Catastrophe | FLORIDA | Florida Hurricane Catastrophe Fund [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Retention Policy, Participation Rate	45.00%
Reinsurance, Aggregate Value of Property Covered Under Contracts	$ 786,700
Reinsurance, Losses Not Covered Prior to Coverage Beginning	246,002
Aggregate Coverage for Covered Losses Under Reinsurance Contract	354,015
Second And Subsequent Catastrophic Events
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	100,000
Second And Subsequent Catastrophic Events | Maximum [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	$ 1,515,197