Other Income (Expense) - Claim Settlement and Sale (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Mar. 24, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Other income (expense)
Effective interest rate (as a percent)					4.90%
Claim settlement				$ 12,548
Gain on sale of assets			$ 9,800
PCR Rentals Sale | Disposed of by Sale
Other income (expense)
Consideration received from sale of assets		$ 9,900	$ 9,900
Gain on sale of assets		$ 9,800
BP Exploration & Production Inc.
Other income (expense)
Claim settlement	$ 13,200			$ 12,500