Property and Equipment - Summary of Property and Equipment by Classification (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2014
Property, Plant and Equipment
Total cost	$ 4,575,661us-gaap_PropertyPlantAndEquipmentGross	$ 4,568,153us-gaap_PropertyPlantAndEquipmentGross
Less: Accumulated depreciation	(564,970)	(601,125)
Property and equipment, net	4,010,691us-gaap_PropertyPlantAndEquipmentNet	3,967,028us-gaap_PropertyPlantAndEquipmentNet
Drilling vessels and equipment
Property, Plant and Equipment
Total cost	4,026,004	4,181,774
Construction work in progress
Property, Plant and Equipment
Total cost	471,046	319,548
Drill pipe
Property, Plant and Equipment
Total cost	42,576	31,265
Office equipment and other
Property, Plant and Equipment
Total cost	$ 36,035	$ 35,566

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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

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-Name Accounting Standards Codification

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- Definition

Amount before accumulated depreciation, depletion and amortization of 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, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ 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

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