Other Financial Statement Disclosures - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
REVENUES	$ 320.2	$ 611.8	$ 694.5	$ 1,112.0
Supplemental Cash Flow Information
Accrued capital expenditures			12.8	21.1
Income Taxes
Provision (benefit) for income taxes	$ 21.4	$ 22.8	$ 51.1	$ 26.9
Effective tax rate	(294.30%)	9.50%	156.30%	7.30%
Increase (decrease) in income tax expense as compared to prior year periods	$ (1.4)		$ 24.2
Cobalt International [Member] | RowanReliance [Member]
Deferred Revenue Arrangement [Line Items]
REVENUES			$ 28.6
Deferred Revenue					$ 95.9
Cobalt International [Member] | RowanReliance [Member] | Deferred Revenue [Domain]
Deferred Revenue Arrangement [Line Items]
Deferred Revenue					$ 95.9