Income Taxes (Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued liabilities	$ 9,287	$ 8,119
Federal NOLs	35,417	43,654
Foreign NOLs	2,338	1,962
State NOLs	10,796	12,382
Tax credit carryforwards	2,159	1,941
Charitable contribution	910	1,340
Valuation allowance	(4,786)	(4,294)
Total deferred tax assets	56,121	65,104
Depreciation and amortization	(78,967)	(89,966)
Other liabilities		(699)
Total deferred tax liabilities	(78,967)	(90,665)
Net noncurrent deferred tax liabilities	$ (22,846)	$ (25,561)