Income Taxes Deferred Tax Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	$ 1,737	$ 3,785
Deferred Tax Liabilities, Noncurrent	(65,488)	(94,657)
Deferred Tax Liabilities, Net	$ (63,751)	$ (90,872)