Business Segments (Geographic Segment Information) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 3,426.1	$ 3,335.7	$ 3,158.5	$ 3,130.3	$ 3,726.8	$ 3,335.1	$ 3,434.2	$ 2,913.0	$ 13,050.6	$ 13,409.1	$ 12,552.9
Property, Plant and Equipment, Net	2,861.8				3,162.0				2,861.8	3,162.0
Russia
Segment Reporting Information [Line Items]
Revenues									2,451.5	2,378.0	2,773.3
Norway
Segment Reporting Information [Line Items]
Revenues									1,393.5	1,371.1	1,202.6
Property, Plant and Equipment, Net	312.2				333.0				312.2	333.0
Brazil
Segment Reporting Information [Line Items]
Revenues									698.8	1,099.7	1,478.7
Property, Plant and Equipment, Net	260.0				313.2				260.0	313.2
ISRAEL
Segment Reporting Information [Line Items]
Revenues									333.6	757.0	243.8
UNITED KINGDOM
Segment Reporting Information [Line Items]
Revenues									513.8	540.8	442.1
Property, Plant and Equipment, Net	936.2				957.1				936.2	957.1
UNITED STATES
Segment Reporting Information [Line Items]
Revenues									2,141.4	1,931.2	1,275.8
Property, Plant and Equipment, Net	467.5				558.1				467.5	558.1
INDIA
Segment Reporting Information [Line Items]
Revenues									386.4	518.0	214.0
ANGOLA
Segment Reporting Information [Line Items]
Revenues									488.5	447.8	385.7
AUSTRALIA
Segment Reporting Information [Line Items]
Revenues									320.8	372.8	926.6
UNITED ARAB EMIRATES
Segment Reporting Information [Line Items]
Revenues									147.9	327.2	460.3
MALAYSIA
Segment Reporting Information [Line Items]
Revenues									281.7	283.8	362.3
CHINA
Segment Reporting Information [Line Items]
Revenues									151.4	272.9	112.3
INDONESIA
Segment Reporting Information [Line Items]
Revenues									286.9	237.6	130.7
NETHERLANDS
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	419.5				493.0				419.5	493.0
All Other Countries
Segment Reporting Information [Line Items]
Revenues									1,094.2	2,114.0	2,209.5
Property, Plant and Equipment, Net	$ 466.4				$ 507.6				466.4	507.6
EGYPT
Segment Reporting Information [Line Items]
Revenues									445.9	177.6	13.2
MOZAMBIQUE
Segment Reporting Information [Line Items]
Revenues									391.4	166.1	116.2
SENEGAL
Segment Reporting Information [Line Items]
Revenues									353.0	176.5	1.2
VIET NAM
Segment Reporting Information [Line Items]
Revenues									340.7	72.1	34.7
GUYANA
Segment Reporting Information [Line Items]
Revenues									330.1	7.2	7.6
SINGAPORE
Segment Reporting Information [Line Items]
Revenues									312.2	64.9	23.4
FRANCE
Segment Reporting Information [Line Items]
Revenues									$ 186.9	$ 92.8	$ 138.9