Business Segment Information (Geographic Segment Information) (Details) (USD $) In Millions, 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]
Revenue	$ 2,156.2	$ 1,976.7	$ 1,985.3	$ 1,824.4	$ 2,047.8	$ 1,724.5	$ 1,707.9	$ 1,646.0	$ 7,942.6	$ 7,126.2	$ 6,151.4
Total Long-lived Assets	1,458.4				1,349.1				1,458.4	1,349.1
United States
Segment Reporting Information [Line Items]
Revenue									2,245.3	1,940.4	1,541.6
Total Long-lived Assets	490.5				443.4				490.5	443.4
Norway
Segment Reporting Information [Line Items]
Revenue									1,023.3	1,217.7	1,231.1
Total Long-lived Assets	250.8				223.3				250.8	223.3
Brazil
Segment Reporting Information [Line Items]
Revenue									831.6	689.0	561.2
Total Long-lived Assets	169.1				166.3				169.1	166.3
Angola
Segment Reporting Information [Line Items]
Revenue									627.0	335.0	192.7
Angola
Segment Reporting Information [Line Items]
Revenue									406.7	516.0	598.0
United Kingdom
Segment Reporting Information [Line Items]
Total Long-lived Assets	147.0				137.2				147.0	137.2
Malaysia
Segment Reporting Information [Line Items]
Total Long-lived Assets	112.6				100.8				112.6	100.8
All other countries
Segment Reporting Information [Line Items]
Revenue									2,808.7	2,428.1	2,026.8
Total Long-lived Assets	$ 288.4				$ 278.1				$ 288.4	$ 278.1