Goodwill and Other Intangible Assets (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)	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	(111,084,000)		(111,084,000)		(107,108,000)
Total	16,845,000		16,845,000		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	147,945,000		147,945,000		$ 151,921,000
Total amortization expense	2,000,000	$ 2,300,000	$ 4,000,000	$ 5,300,000
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	(109,701,000)		(109,701,000)		(105,911,000)
Total	16,127,000		16,127,000		19,917,000
Non-compete agreements
Other intangible assets
Cost	2,101,000		2,101,000		2,101,000
Accumulated Amortization	(1,383,000)		(1,383,000)		(1,197,000)
Total	$ 718,000		$ 718,000		$ 904,000