Drilling and Other Property and Equipment (Details) (USD $)	Sep. 30, 2011	Aug. 01, 2011 Drillships	Dec. 31, 2010
Summary of cost and accumulated depreciation of drilling and other property and equipment
Drilling rigs and equipment	$ 7,298,695,000		$ 7,163,196,000
Construction work-in-progress	483,046,000		0
Land and buildings	60,449,000		56,536,000
Office equipment and other	47,622,000		44,689,000
Cost	7,889,812,000		7,264,421,000
Less: accumulated depreciation	(3,284,064,000)		(2,980,629,000)
Drilling and other property and equipment, net	4,605,748,000		4,283,792,000
Drilling and Other Property and Equipment (Textual) [Abstract]
Transfer of deposits related to construction of drillship into work in progress		478,300,000
Number of drillships under construction		3
Accrued drillship construction installment	$ 0		$ 154,427,000

Accrued drillship construction installment.

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Drilling and other property and equipment.

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Land and Buildings.

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Number of drillships under construction.

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Summary of cost and accumulated depreciation of drilling and other property and equipment.

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Transfer of deposits related to construction of drillship into work in progress.

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The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

+ References

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Gross amount, at the balance sheet date, of long-lived assets under construction that include construction costs to date on capital projects that have not been completed and assets being constructed that are not ready to be placed into service.

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Gross amount, at the balance sheet date, of long-lived, depreciable assets commonly used in offices and stores. Examples include desks, chairs, and store fixtures.

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Gross amount, as of the balance sheet date, of long-lived, depreciable assets used in the production process to produce goods and services.

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Gross amount, at the balance sheet date, of long-lived physical assets used in the normal conduct of business and not intended for resale. This can include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

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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, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

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