Property and Equipment (A Summary of Property and Equipment by Classification) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012
Property, Plant and Equipment [Line Items]
Cost	$ 3,346,006	$ 3,002,162
Less: Accumulated depreciation	(491,491)	(464,822)
Drilling and other property and equipment, net	2,854,515	2,537,340
Drilling vessels and equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	2,727,429	2,523,895
Construction work in progress [Member]
Property, Plant and Equipment [Line Items]
Cost	575,820	438,081
Drill pipe [Member]
Property, Plant and Equipment [Line Items]
Cost	20,658	20,576
Office equipment and other [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 22,099	$ 19,610

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.

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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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