Schedule IV Reinsurance (Details) - USD ($)		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount										$ 1,244,870,000		$ 1,074,298,000		$ 990,016,000
Ceded to Other Companies	[1]									109,903,000		67,195,000		57,271,000
Assumed from Other Companies										10,382,000	[2]	6,904,000	[2]	28,000
Net Amount		$ 301,486,000	$ 281,185,000	$ 299,166,000	$ 263,512,000	$ 261,682,000	$ 258,431,000	$ 251,344,000	$ 242,550,000	$ 1,145,349,000		$ 1,014,007,000		$ 932,773,000
Assumed Premium as a Percentage of Net Premiums										0.91%		0.68%		0.00%

[1] Net of profit commission.

[2] Includes premiums earned from our participation in certain credit risk transfer programs.