Business Segment Information (Geographic Segment Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenue	$ 1,840.9	$ 1,419.0	$ 1,494.9	$ 1,396.6	$ 1,500.5	$ 1,287.2	$ 1,229.4	$ 1,081.9	$ 6,151.4	$ 5,099.0	$ 4,125.6
Long-lived assets	1,243.5				767.9				1,243.5	767.9	609.0
United States
Segment Reporting Information [Line Items]
Revenue									1,541.6	1,156.4	939.9
Long-lived assets	424.0				238.7				424.0	238.7	185.3
Norway
Segment Reporting Information [Line Items]
Revenue									1,231.1	966.0	703.4
Long-lived assets	197.4				169.7				197.4	169.7	153.7
Angola
Segment Reporting Information [Line Items]
Revenue									598.0	514.4	564.7
Brazil
Segment Reporting Information [Line Items]
Revenue									561.2	541.9	360.1
Long-lived assets	161.4				126.2				161.4	126.2	93.3
Canada
Segment Reporting Information [Line Items]
Long-lived assets	107.3				6.0				107.3	6.0	3.2
All other countries
Segment Reporting Information [Line Items]
Revenue									2,219.5	1,920.3	1,557.5
Long-lived assets	$ 353.4				$ 227.3				$ 353.4	$ 227.3	$ 173.5