Acquisition of Interstate Distributor Co. (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 06, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual, Percent		$ 5,659	$ 3,882
Payments to Acquire Intangible Assets	$ 6,316
Cash Acquired from Acquisition	6,316
Business Acquisition, Pro Forma Revenue		756,498	938,007
Business Acquisition, Pro Forma Net Income (Loss)		72,752	54,222
Accounts and Other Receivables, Net, Current	35,131
Other current assets	2,426	13,782	13,841
Property, Plant and Equipment, Net	71,964	442,862	407,648
Other Assets, Noncurrent	1,244	24,261	12,382
Intangible Assets, Current	7,800
Goodwill	32,198	132,410	100,212
Assets	157,079	789,127	738,228
Business Combination, Consideration Transferred	93,044
Payments to Acquire Businesses, Net of Cash Acquired	86,728	86,728	$ 0	$ 0
Business Combination, Acquisition Related Costs		$ 900
Accounts Payable and Accrued Liabilities	35,209
Self Insurance Reserve	10,826
Cash [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 93,044