Acquisition of Interstate Distributor Co. (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 06, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Business Acquisition, Contingent Consideration [Line Items]
Restricted Cash and Cash Equivalents		$ 32,500		$ 32,500		$ 21,700
Business Acquisition, Pro Forma Revenue				590,794		938,007
Operating Revenue		$ 182,114	$ 149,316	$ 441,632	$ 472,893
Cash Acquired from Acquisition	$ 6,316
Business Combination, Recognized Identifiable Assets Acquired, Percent of Total Assets in Combined Entity		20.30%		20.30%
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual, Percent		33.00%		13.60%
Business Combination, Acquisition Related Costs		$ 500		$ 900
Business Acquisition, Pro Forma Net Income (Loss)				34,148		54,222
Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed)				83,903
Property, Plant, and Equipment, Fair Value Disclosure		(33,349)		(33,349)
Noncash or Part Noncash Acquisition, Value of Assets Acquired				(2,822)
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed				9,546
Fair Value of Assets Acquired				57,278
Noncash or Part Noncash Acquisition, Intangible Assets Acquired				4,700
Accounts and Other Receivables, Net, Current	35,131
Other current assets	3,333	30,656		30,656		13,841
Property, Plant and Equipment, Net	71,964	454,278		454,278		407,648
Other Assets, Noncurrent	1,244	22,821		22,821		12,382
Intangible Assets, Current	4,700
GOODWILL	31,973	132,185		132,185		100,212
Assets	154,661	797,694		797,694		738,228
Accounts Payable and Accrued Liabilities	(31,884)
Self Insurance Reserve	(10,826)
Long-term Debt	(17,404)
Other accruals	(596)	(13,647)		(13,647)		$ (10,727)
Payments to Acquire Intangible Assets	(6,316)
Payments to Acquire Businesses, Net of Cash Acquired	87,635			87,635	$ 0
Business Combination, Consideration Transferred	93,951
Insurance Claims [Member]
Business Acquisition, Contingent Consideration [Line Items]
Restricted Cash and Cash Equivalents		$ 6,100		$ 6,100
Cash [Member]
Business Acquisition, Contingent Consideration [Line Items]
Payments to Acquire Businesses, Gross	$ 93,951