Segment Information (Schedule Of Segment Reporting Information) (Details) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenues	$ 915.6	$ 428.3	$ 1,841.3	$ 1,288.3
Operating expenses - Contract drilling (exclusive of depreciation)	477.5	194.1	955.4	582.5
Depreciation	135.8	55.6	278.8	159.2
General and administrative	40.8	20.6	118.3	63.2
OPERATING INCOME	261.5	158.0	488.8	483.4
Property and equipment, net	12,311.7	4,986.1	12,311.7	4,986.1	5,049.9
Deepwater [Member]
Segment Reporting Information [Line Items]
Revenues	440.4	110.5	770.8	361.8
Operating expenses - Contract drilling (exclusive of depreciation)	233.0	48.0	385.0	139.5
Depreciation	73.5	11.7	123.7	31.2
General and administrative
OPERATING INCOME	133.9	50.8	262.1	191.1
Property and equipment, net	8,981.7	2,769.8	8,981.7	2,769.8
Midwater [Member]
Segment Reporting Information [Line Items]
Revenues	121.3		157.5
Operating expenses - Contract drilling (exclusive of depreciation)	72.1		95.0
Depreciation	15.7		20.9
General and administrative
OPERATING INCOME	33.5		41.6
Property and equipment, net	904.1		904.1
Jackup [Member]
Segment Reporting Information [Line Items]
Revenues	330.1	317.8	882.7	926.5
Operating expenses - Contract drilling (exclusive of depreciation)	154.7	145.6	450.4	429.7
Depreciation	44.2	43.2	129.8	125.2
General and administrative
OPERATING INCOME	131.2	129.0	302.5	371.6
Property and equipment, net	2,376.7	2,197.5	2,376.7	2,197.5
Other [Member]
Segment Reporting Information [Line Items]
Revenues	23.8		30.3
Operating expenses - Contract drilling (exclusive of depreciation)	17.7	0.5	25.0	13.3
Depreciation	0.6	0.4	1.5	1.9
General and administrative
OPERATING INCOME	5.5	(0.9)	3.8	(15.2)
Property and equipment, net	26.6	14.8	26.6	14.8
Operating Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	915.6	428.3	1,841.3	1,288.3
Operating expenses - Contract drilling (exclusive of depreciation)	477.5	194.1	955.4	582.5
Depreciation	134.0	55.3	275.9	158.3
General and administrative
OPERATING INCOME	304.1	178.9	610.0	547.5
Property and equipment, net	12,289.1	4,982.1	12,289.1	4,982.1
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Revenues
Operating expenses - Contract drilling (exclusive of depreciation)
Depreciation	1.8	0.3	2.9	0.9
General and administrative	40.8	20.6	118.3	63.2
OPERATING INCOME	(42.6)	(20.9)	(121.2)	(64.1)
Property and equipment, net	$ 22.6	$ 4.0	$ 22.6	$ 4.0

The expense recognized in the current period that allocates the cost of a tangible asset used in providing revenue generating services over the asset's useful life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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