Segment Information (Schedule Of Segment Reporting Information) (Details) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 1,163,900,000us-gaap_RevenueOilAndGasServices	$ 1,066,700,000us-gaap_RevenueOilAndGasServices
Operating Expenses [Abstract]
Contract drilling (exclusive of depreciation)	518,300,000us-gaap_CostOfServicesOilAndGas	520,200,000us-gaap_CostOfServicesOilAndGas
Depreciation	137,100,000us-gaap_CostOfServicesDepreciation	131,100,000us-gaap_CostOfServicesDepreciation
General and administrative	30,100,000us-gaap_GeneralAndAdministrativeExpense	38,100,000us-gaap_GeneralAndAdministrativeExpense
OPERATING (LOSS) INCOME	478,400,000us-gaap_OperatingIncomeLoss	377,300,000us-gaap_OperatingIncomeLoss
Property and equipment, net	12,725,300,000us-gaap_PropertyPlantAndEquipmentNet	14,418,300,000us-gaap_PropertyPlantAndEquipmentNet	12,534,800,000us-gaap_PropertyPlantAndEquipmentNet
Floaters [Member]
Segment Reporting Information [Line Items]
Revenues	695,000,000	651,600,000
Operating Expenses [Abstract]
Contract drilling (exclusive of depreciation)	293,500,000	306,600,000
Depreciation	93,000,000	90,700,000
General and administrative	0	0
OPERATING (LOSS) INCOME	308,500,000	254,300,000
Property and equipment, net	9,453,500,000	11,376,200,000
Jackups Member
Segment Reporting Information [Line Items]
Revenues	428,300,000	398,500,000
Operating Expenses [Abstract]
Contract drilling (exclusive of depreciation)	191,500,000	202,300,000
Depreciation	41,500,000	38,500,000
General and administrative	0	0
OPERATING (LOSS) INCOME	195,300,000	157,700,000
Property and equipment, net	3,195,200,000	2,986,100,000
Other [Member]
Segment Reporting Information [Line Items]
Revenues	40,600,000	16,600,000
Operating Expenses [Abstract]
Contract drilling (exclusive of depreciation)	33,300,000	11,300,000
Depreciation	0	0
General and administrative	0	0
OPERATING (LOSS) INCOME	7,300,000	5,300,000
Property and equipment, net	0	0
Operating Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	1,163,900,000	1,066,700,000
Operating Expenses [Abstract]
Contract drilling (exclusive of depreciation)	518,300,000	520,200,000
Depreciation	134,500,000	129,200,000
General and administrative	0	0
OPERATING (LOSS) INCOME	511,100,000	417,300,000
Property and equipment, net	12,648,700,000	14,362,300,000
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Operating Expenses [Abstract]
Contract drilling (exclusive of depreciation)	0	0
Depreciation	2,600,000	1,900,000
General and administrative	30,100,000	38,100,000
OPERATING (LOSS) INCOME	(32,700,000)	(40,000,000)
Property and equipment, net	$ 76,600,000	$ 56,000,000

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 Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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

-Publisher FASB

-Name Accounting Standards Codification

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-Section S99

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Costs of generating 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

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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

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

-Publisher FASB

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+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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

-Publisher FASB

-Name Accounting Standards Codification

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

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-Name Regulation S-X (SX)

-Number 210

-Section 02

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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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.

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

-Publisher FASB

-Name Accounting Standards Codification

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