Acquisition of Interstate Distributor Co. (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 06, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 93,044
Cash Acquired from Acquisition	6,316
Business Combination, Acquisition Related Costs			$ 900
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual, Percent			5,700	$ 3,900
Business Acquisition, Pro Forma Revenue			756,498	938,007
Business Acquisition, Pro Forma Net Income (Loss)			72,752	54,222
Payments to Acquire Intangible Assets	6,316
Accounts and Other Receivables, Net, Current	35,131
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	2,426
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	71,964
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	1,244
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	7,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	157,079
Self Insurance Reserve	10,826
Payments to Acquire Businesses, Net of Cash Acquired	86,728	$ 0	$ 86,728	$ 0
Accounts Payable and Accrued Liabilities	35,209
Long-term Debt	17,404
Business Combination, Consideration Transferred	93,044
Accounts Payable and Accrued Liabilities [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	596
Cash [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	93,000
Goodwill
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	$ 32,198