Reinsurance (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Premiums Written [Abstract]
Direct										$ 546,708	$ 574,181	$ 581,070
Ceded on direct										(106,561)	(122,676)	(138,102)
Net direct										440,147	451,505	442,968
Assumed										853	737	1,430
Ceded on assumed										0	0	0
Net assumed										853	737	1,430
Net										441,000	452,242	444,398
Premiums Earned [Abstract]
Direct										557,795	570,959	562,364
Ceded on direct	[1]									(113,125)	(124,446)	(131,080)
Net direct										444,670	446,513	431,284
Assumed										845	775	1,596
Ceded on assumed										0	0	0
Net assumed										845	775	1,596
Net		$ 120,273	$ 117,853	$ 97,730	$ 109,659	$ 111,357	$ 110,288	$ 115,631	$ 110,012	445,515	447,288	432,880
Net losses and loss expenses incurred reduced by ceded reinsurance recoveries										105,895	121,927	148,173
Net losses and loss expenses incurred from reinsurance assumed from non-affiliates										432	193	$ 1,300
Components of reinsurance recoverable [Abstract]
Case unpaid losses, net of allowance for reinsurance		166,171				166,675				166,171	166,675
Incurred but not reported unpaid losses and loss expenses		257,225				230,459				257,225	230,459
Paid losses and loss expenses		24,133				20,334				24,133	20,334
Unearned premiums		8,035				14,599				8,035	14,599
Reinsurance recoverable		$ 455,564				$ 432,067				$ 455,564	$ 432,067

[1] Included in Ceded to Other Companies is $0 for each of 2020, 2019 and 2018 relating to retrocessions associated with premiums assumed from other companies.  Percentage of Amount Assumed to Net above considers the impact of this retrocession.