Acquisitions of Millis Transfer and Interstate Distributor Co. (Details) - USD ($) $ in Thousands			12 Months Ended
	Aug. 26, 2019	Jul. 06, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			$ 500		$ 900
Accounts and Other Receivables, Net, Current	$ 14,474
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	1,656
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	117,060
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	802
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	15,300
Business Combination, Recognized Identifiable Assets Acquired, Goodwill	35,885
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	185,177
Self Insurance Reserve	4,371
Payments to Acquire Businesses, Net of Cash Acquired	61,927		$ 61,927	$ 0	86,728
Accounts Payable and Accrued Liabilities	31,737
Long-term Debt	70,191
Business Combination, Total Consideration	156,000
Business Combination, Cash and Equity Transferred	62,677
Noncash or Part Noncash Acquisition, Debt Assumed	93,300
Acquired Business Percent of Assets			21.10%
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	750
Deferred Taxes	$ 16,201
Debt, Long-term and Short-term, Combined Amount			$ 0
Acquired Business Percent of Revenue			8.80%
Payments to Acquire Businesses, Gross		$ 93,000
Cash Acquired from Acquisition		$ 6,300
Business Combination, Pro Forma Information, Net Income Change			$ 3,000	3,600	5,700
Business Acquisition, Pro Forma Revenue			694,672	760,917	756,498
Business Acquisition, Pro Forma Net Income (Loss)			$ 75,951	$ 76,259	$ 72,752