Inventories (Schedule of Inventory) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Inventories [Abstract]
Unsold crude oil	$ 17,146	$ 25,583
Materials and supplies	109,925	141,205
Inventory, Net, Total	$ 127,071	$ 166,788	[1]

[1] Reclassified to conform to current presentation. See Note B for additional information.