Operations by Business Segment and Geographic Area - Revenues and Long-Lived Assets by Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 3,062,754	$ 3,659,624	$ 3,287,019
Long-Lived Assets	1,861,938	1,744,498	1,642,363
Africa [Member]
Segment Reporting Information [Line Items]
Revenues	659,038	795,229	696,202
Long-Lived Assets	205,440	215,122	186,865
Foreign [Member]
Segment Reporting Information [Line Items]
Revenues	1,757,317	2,342,279	2,180,381
Long-Lived Assets	791,097	906,225	950,959
Norway [Member]
Segment Reporting Information [Line Items]
Revenues	250,272	488,789	461,915
Long-Lived Assets	274,868	332,503	429,603
United Kingdom [Member]
Segment Reporting Information [Line Items]
Revenues	367,326	456,804	383,397
Long-Lived Assets	138,327	113,191	99,250
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Revenues	245,978	317,277	335,129
Long-Lived Assets	71,438	90,061	83,885
Brazil [Member]
Segment Reporting Information [Line Items]
Revenues	118,056	185,299	213,282
Long-Lived Assets	57,896	99,269	112,840
Other [Member]
Segment Reporting Information [Line Items]
Revenues	116,647	98,881	90,456
Long-Lived Assets	43,128	56,079	38,516
United States [Member]
Segment Reporting Information [Line Items]
Revenues	1,305,437	1,317,345	1,106,638
Long-Lived Assets	$ 1,070,841	$ 838,273	$ 691,404