Segment Information (Schedule Of Segment Reporting Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2011	Mar. 31, 2010	Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenues	$ 361.5	$ 448.6
Operating expenses Contract drilling (exclusive of depreciation)	191.6	182.4
Depreciation	59.5	51.7
General and administrative	30.1	20.6
Operating income (loss)	80.3	193.9
Property and equipment, net	5,259.1	4,482.6	5,049.9
Deepwater [Member]
Segment Reporting Information [Line Items]
Revenues	98.2	130.4
Operating expenses Contract drilling (exclusive of depreciation)	40.9	45.0
Depreciation	16.3	9.8
Operating income (loss)	41.0	75.6
Property and equipment, net	3,008.7	2,341.5
Midwater [Member]
Segment Reporting Information [Line Items]
Revenues
Operating expenses Contract drilling (exclusive of depreciation)
Depreciation
General and administrative
Operating income (loss)
Property and equipment, net
Jackup [Member]
Segment Reporting Information [Line Items]
Revenues	263.3	318.2
Operating expenses Contract drilling (exclusive of depreciation)	150.3	137.0
Depreciation	42.4	40.9
Operating income (loss)	70.6	140.3
Property and equipment, net	2,232.8	2,108.8
Other [Member]
Segment Reporting Information [Line Items]
Operating expenses Contract drilling (exclusive of depreciation)	0.4	0.4
Depreciation	0.4	0.7
Operating income (loss)	(0.8)	(1.1)
Property and equipment, net	14.0	28.1
Operating Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	361.5	448.6
Operating expenses Contract drilling (exclusive of depreciation)	191.6	182.4
Depreciation	59.1	51.4
Operating income (loss)	110.8	214.8
Property and equipment, net	5,255.5	4,478.4
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Depreciation	0.4	0.3
General and administrative	30.1	20.6
Operating income (loss)	(30.5)	(20.9)
Property and equipment, net	$ 3.6	$ 4.2

Costs incurred and are directly related to generating contract revenues.

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- Definition

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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

+ Details

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- Definition

The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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- Definition

Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, and production equipment.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 13

-Subparagraph a

-Article 5

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 12

-Paragraph 5

-Subparagraph b, c

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 7

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- Definition

Revenue from oil and gas-related services including well services (such as drilling, rigs and analytic evaluations), transportation, and other supporting contractor services, during the reporting period.

+ References

No definition available.

+ Details

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