Business Segment Information - Revenue by Geographical Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total net revenues	$ 157,683	$ 182,462	$ 166,016	$ 189,641	$ 207,160	$ 340,837	$ 305,587	$ 253,572	$ 695,802	$ 1,107,156	$ 876,561
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues									298,391	403,994	345,525
North Sea [Member]
Segment Reporting Information [Line Items]
Total net revenues									263,438	504,016	403,816
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues									187,700	362,700	327,100
Other [Member]
Segment Reporting Information [Line Items]
Total net revenues									$ 133,973	$ 199,146	$ 127,220