Summary Of Significant Accounting Policies (Estimated Useful Lives Of Assets) (Details)	12 Months Ended
Sep. 30, 2011
Drilling Vessels And Related Equipment [Member]
Estimated useful lives of asset, Minimum	5
Estimated useful lives of asset, Maximum	35
Drill Pipe [Member]
Estimated useful lives of asset	3
Furniture And Other [Member]
Estimated useful lives of asset, Minimum	3
Estimated useful lives of asset, Maximum	10
Atwood Southern Cross [Member]
Estimated useful lives of asset, Minimum	1
Estimated useful lives of asset	5
Seahawk [Member]
Estimated useful lives of asset, Minimum	1
Estimated useful lives of asset	5

Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2155824

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- Definition

The average useful life of long-lived, physical assets used in the normal conduct of business and not intended for resale. 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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- Definition

The maximum useful life of long-lived, physical assets used in the normal conduct of business and not intended for resale. 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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The minimum useful life of long lived, physical assets used in the normal conduct of business and not intended for resale. 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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