Income Taxes - Income Tax Temporary Differences Table (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Depreciable property	$ (4,976)	$ (138,159)
Credit carryforwards	498	512
Other intangible assets	(1,928)	(2,070)
Other	4	13
Net long-term deferred income tax liabilities	$ (6,402)	$ (139,704)