Property and Equipment (A Summary of Property and Equipment by Classification) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Sep. 30, 2012
Property, Plant and Equipment [Line Items]
Cost	$ 3,585,814	$ 3,002,162
Less: Accumulated depreciation	(550,242)	(464,822)
Drilling and other property and equipment, net	3,035,572	2,537,340
Drilling vessels and equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	2,968,358	2,523,895
Construction work in progress [Member]
Property, Plant and Equipment [Line Items]
Cost	573,010	438,081
Drill pipe [Member]
Property, Plant and Equipment [Line Items]
Cost	21,439	20,576
Office equipment and other [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 23,007	$ 19,610