Fair Value Measurements - Concentration of Credit Risk (Details) - Customer Concentration Risk [Member]	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Deepwater Segment [Member] | Anadarko [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	0.00%		19.00%
Deepwater Segment [Member] | Anadarko [Member] | Sales Revenue, Services, Net [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	18.00%	16.00%
Deepwater Segment [Member] | Cobalt International [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	0.00%		0.00%
Deepwater Segment [Member] | Cobalt International [Member] | Sales Revenue, Services, Net [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	0.00%	14.00%
Jack-ups and Unallocated and Other [Member] | ARO Drilling [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	23.00%		9.00%
Jack-ups and Unallocated and Other [Member] | ARO Drilling [Member] | Sales Revenue, Services, Net [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	12.00%	0.00%
Jack-ups [Member] | Saudi Aramco [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	43.00%		34.00%
Jack-ups [Member] | Saudi Aramco [Member] | Sales Revenue, Services, Net [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	34.00%	29.00%
Jack-ups [Member] | Shell [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	12.00%		0.00%
Jack-ups [Member] | Shell [Member] | Sales Revenue, Services, Net [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	6.00%	0.00%