Acquisitions Pro Forma (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended								12 Months Ended
	Apr. 03, 2017	Apr. 29, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues			$ 181,089	$ 187,652	$ 183,148	$ 180,127	$ 182,586	$ 171,128	$ 178,073	$ 122,633	$ 723,942	$ 654,420	$ 487,117
Pro Forma Revenue													662,149
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			$ (10,968)	$ (11,707)	$ 14,701	$ 8,369	$ 27,001	$ (28,012)	$ 7,257	$ 3,899	$ 394	$ 10,145	5,698
Pro Forma Net Income (Loss)													$ 37,658
Earnings Per Share, Diluted			$ (0.26)	$ (0.27)	$ 0.34	$ 0.20	$ 0.63	$ (0.66)	$ 0.17	$ 0.18	$ 0.01	$ 0.27	$ 0.26
Pro Forma Earnings Per Share, Diluted													$ 0.88
AmCo Holding Company
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro Forma Revenue	$ 38,096											$ 692,516	$ 175,032
Pro Forma Net Income (Loss)	$ 6,712											$ 16,857	$ 31,960
Pro Forma Earnings Per Share, Diluted	$ 0.00											$ 0.39	$ 0.00
Interboro Insurance Company
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro Forma Revenue		$ 18,963											$ 506,080
Pro Forma Net Income (Loss)		$ 8,187											$ 13,885
Pro Forma Earnings Per Share, Diluted		$ 0.38											$ 0.64