Business Segment Information (Revenue By Geographical Region) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total net revenues	$ 207,160	$ 340,837	$ 305,587	$ 253,572	$ 226,837	$ 220,117	$ 232,178	$ 197,429	$ 1,107,156	$ 876,561	$ 846,109
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues									403,994	345,525	281,308
North Sea [Member]
Segment Reporting Information [Line Items]
Total net revenues									504,016	403,816	345,074
North Sea [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues									362,700	327,100	283,100
Other [Member]
Segment Reporting Information [Line Items]
Total net revenues									$ 199,146	$ 127,220	$ 219,727