Schedule IV Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned									$ 990,016	$ 999,093	$ 973,645
Ceded Premiums Earned									57,271	77,359	57,780
Assumed Premiums Earned									28	35	43
Net premiums earned—insurance	$ 245,175	$ 236,702	$ 229,096	$ 221,800	$ 233,585	$ 238,149	$ 229,085	$ 220,950	$ 932,773	$ 921,769	$ 915,908
Premiums, Percentage Assumed to Net									0.00%	0.00%	0.00%