Consolidated Statements Of Income (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
OPERATING REVENUES	$ 4,300.7	$ 2,797.7	$ 1,674.2
OPERATING EXPENSES
Contract drilling (exclusive of depreciation)	2,028.0	1,449.1	741.8
Depreciation	558.6	408.9	210.4
General and administrative	148.9	158.6	86.1
Total operating expenses	2,735.5	2,016.6	1,038.3
OPERATING INCOME	1,565.2	781.1	635.9
OTHER INCOME (EXPENSE)
Interest income	22.8	17.2	0.7
Interest expense, net	(123.6)	(95.9)	0
Other, net	2.2	20.8	17.5
Other income (expense), net	(98.6)	(57.9)	18.2
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	1,466.6	723.2	654.1
PROVISION FOR INCOME TAXES
Current income tax expense	226.4	134.9	80.5
Deferred income tax expense (benefit)	18.0	(19.5)	16.7
Total provision for income taxes	244.4	115.4	97.2
INCOME FROM CONTINUING OPERATIONS	1,222.2	607.8	556.9
DISCONTINUED OPERATIONS
Loss from discontinued operations, net	(29.0)	(4.0)	(9.6)
(Loss) gain on disposal of discontinued operations, net	(16.5)	1.8	38.6
DISCONTINUED OPERATIONS, NET	(45.5)	(2.2)	29.0
NET INCOME	1,176.7	605.6	585.9
NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	(7.0)	(5.2)	(6.4)
NET INCOME ATTRIBUTABLE TO ENSCO	1,169.7	600.4	579.5
EARNINGS PER SHARE - BASIC
Continuing operations	$ 5.24	$ 3.10	$ 3.86
Discontinued operations	$ (0.19)	$ (0.01)	$ 0.20
Total earnings per share - basic	$ 5.05	$ 3.09	$ 4.06
EARNINGS PER SHARE - DILUTED
Continuing operations	$ 5.23	$ 3.09	$ 3.86
Discontinued operations	$ (0.19)	$ (0.01)	$ 0.20
Total earnings per share - diluted	$ 5.04	$ 3.08	$ 4.06
NET INCOME ATTRIBUTABLE TO ENSCO SHARES - BASIC AND DILUTED	$ 1,157.4	$ 593.5	$ 572.1
WEIGHTED-AVERAGE SHARES OUTSTANDING
Basic	229.4	192.2	141.0
Diluted	229.7	192.6	141.0
CASH DIVIDENDS PER SHARE	$ 1.5	$ 1.40	$ 1.075