Commitments and Contingencies (Details) (USD $)	6 Months Ended
	Jun. 30, 2012 Contract Installment	Jun. 30, 2011	May 31, 2012	Dec. 31, 2011
Commitments and Contingencies (Textual) [Abstract]
Deductible for marine liability coverage including personal injury claims, per first occurrence	$ 10,000,000
Range of deductible for liability coverage for personal injury claims, lower limit	5,000,000
Range of deductible for liability coverage for personal injury claims, upper limit	100,000,000
Estimated liability for personal injury claims	37,300,000			32,700,000
Reserve for personal injury claims recorded in accrued liabilities	10,600,000			10,100,000
Reserve for personal injury claims recorded in other liabilities	26,700,000			22,600,000
Total unconditional purchase obligation for Onyx Project	300,000,000
Total number of installments due under vessel modification agreement	11
Total number of installments due under each drillship turnkey construction agreement	2
Number of turnkey contracts for drillship construction	4
Total unconditional purchase obligation for drillships			2,600,000,000
Vessel modification agreement Payment during the period	36,500,000
First Installments on Drillships aggregate amount	169,300,000	478,300,000
Other Purchase obligations	0			0
Contingent liability under letters of credit and other bonds	125,400,000
Performance bonds that may require collateral at any time	$ 107,000,000