Subsequent Events (Details) (USD $)	9 Months Ended
	Sep. 30, 2012 item
Subsequent Events | Norway Tax Investigations
Subsequent Events
Number of subsidiaries against which advisory opinion have been issued	1
Subsequent Events | Three Year Secured Revolving Credit Facility
Subsequent Events
Borrowing capacity, maximum	900,000,000
Term of facility	3 years
Basis of variable interest rate	LIBOR
Maximum debt to tangible capitalization ratio, numerator	0.6
Maximum debt to tangible capitalization ratio, denominator	1
Subsequent Events | Three Year Secured Revolving Credit Facility | Minimum
Subsequent Events
Spread on variable rate basis (as a percent)	0.875%
Commitment fee percentage at period end	0.125%
Subsequent Events | Three Year Secured Revolving Credit Facility | Maximum
Subsequent Events
Spread on variable rate basis (as a percent)	2.50%
Commitment fee percentage at period end	0.50%
Drilling Fleet /Standard Jackups GSF Rig 103
Subsequent Events
Carrying value of drilling fleet assets reclassified to assets held for sale	9,000,000