Goodwill and Other Intangible Assets (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) segment
Goodwill
Balance at the beginning of the period			$ 346,168,000
Balance at the end of the period	$ 346,168,000		346,168,000		$ 346,168,000
Goodwill, Impairment Loss			0
Other intangible assets
Cost	127,929,000		127,929,000		127,929,000
Accumulated Amortization	(112,893,000)		(112,893,000)		(107,108,000)
Total	15,036,000		15,036,000		20,821,000
Cost	293,929,000		293,929,000		293,929,000
Accumulated Impairment	(34,900,000)		(34,900,000)		(34,900,000)
Net	146,136,000		146,136,000		$ 151,921,000
Total amortization expense	1,800,000	$ 2,100,000	5,800,000	$ 7,400,000
Intangible asset impairment charge	0	$ 0	$ 0	$ 0
Number of reporting segments | segment			1		3
Trade names
Other intangible assets
Cost	166,000,000		$ 166,000,000		$ 166,000,000
Net	131,100,000		131,100,000		131,100,000
Accumulated Impairment	(34,900,000)		(34,900,000)		(34,900,000)
Customer relationship
Other intangible assets
Cost	125,828,000		125,828,000		125,828,000
Accumulated Amortization	(111,417,000)		(111,417,000)		(105,911,000)
Total	14,411,000		14,411,000		19,917,000
Non-compete agreements
Other intangible assets
Cost	2,101,000		2,101,000		2,101,000
Accumulated Amortization	(1,476,000)		(1,476,000)		(1,197,000)
Total	$ 625,000		$ 625,000		$ 904,000