Business Segment Information - Revenue By Geographical Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total net revenues	$ 128,031	$ 161,245	$ 107,267	$ 91,039	$ 157,683	$ 182,462	$ 166,016	$ 189,641	$ 487,582	$ 695,802	$ 1,107,156
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues									298,279	298,391	403,994
North Sea [Member]
Segment Reporting Information [Line Items]
Total net revenues									137,313	263,438	504,016
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues									123,600	187,700	362,700
Other [Member]
Segment Reporting Information [Line Items]
Total net revenues									$ 51,990	$ 133,973	$ 199,146