NATURE OF OPERATIONS AND BASIS OF PRESENTATION (Details)		1 Months Ended	2 Months Ended	3 Months Ended		10 Months Ended	12 Months Ended
	Oct. 19, 2017 drilling_unit	Jan. 31, 2018 drilling_unit	May 22, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Oct. 16, 2017 segment	Dec. 31, 2017 USD ($) drilling_unit segment $ / bbl $ / d	Dec. 31, 2016 USD ($)	Sep. 15, 2016 USD ($)	May 23, 2016 USD ($)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Number of operating segments | segment						2	3
Number of Drillships | drilling_unit							4
Number of fleet of self-elevating mobile offshore jack-up drilling units | drilling_unit							21
Deferred revenue							$ 1,600,000	$ 114,400,000
Rowan Relentless [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contingent payments, period of evaluation							12 months
Revenue			$ 30,500,000		$ 173,200,000
Revenue, canceled contract value					130,900,000
Revenue, fair value of derivative associated with early contract termination agreement					6,200,000
Recognition of previously deferred revenue					$ 5,600,000
Outstanding Receivables From Early Contract Termination [Member] | Rowan Relentless [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Outstanding receivables from early termination of contract										$ 215,000,000
Contingent Consideration Threshold 1 [Member] | Rowan Relentless [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Additional contingent payments							$ 10,000,000
Contingent payment, threshold price per barrel (in USD per bbl) | $ / bbl							50
Contingent Consideration Threshold 2 [Member] | Rowan Relentless [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Additional contingent payments							$ 20,000,000
Contingent payment, threshold price per barrel (in USD per bbl) | $ / bbl							65
Subsequent Event [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Number of fleet of self-elevating mobile offshore jack-up drilling units purchased | drilling_unit		2
Saudi Arabia Joint Venture [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Number of fleet of self-elevating mobile offshore jack-up drilling units | drilling_unit	5
Cobalt International [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Exclusive provider contract term (in years)							5 years
Deferred revenue								95,900,000
Cobalt International [Member] | Rowan Reliance [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Outstanding receivables from early termination of contract									$ 95,900,000
Day rate (in USD per day) | $ / d							582,000
Day rate, after March 31, 2017 (in USD per day) | $ / d							262,000
Deferred revenue									$ 95,900,000
Cobalt International [Member] | Outstanding Receivables From Early Contract Termination [Member] | Rowan Reliance [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Outstanding receivables from early termination contract, cash received in period				$ 19,600,000				$ 76,300,000