Income Taxes Deferred tax assets and liabilties (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts	$ 224	$ 515
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	3,179	6,550
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	92	156
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Self Insurance	15,415	18,225
Deferred Tax Assets, Operating Loss Carryforwards	0	237
Unrecognized tax benefit	963	1,278
Deferred Tax Assets, Other	2	0
Deferred Tax Assets, Gross	19,875	26,961
Deferred Tax Assets, Valuation Allowance	0	0
Deferred Tax Assets, Net	19,875	26,961
Deferred Tax Liabilities, Property, Plant and Equipment	(74,794)	(81,322)
Deferred Tax Liabilities, Goodwill and Intangible Assets	(10,319)	(7,984)
Deferred Tax Liabilities, Prepaid Expenses	(1,268)	(1,406)
Deferred Income Tax Liabilities	(86,381)	(90,712)
Deferred Tax Liabilities, Net	$ (66,506)	$ (63,751)