Commitments and Contingent Liabilities (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013 drilling_unit lawsuit	Dec. 31, 2009
Status of company's rigs under construction [Abstract]
Total estimated project costs	$ 2,953
Total costs incurred through June 30, 2013	867
Projected costs for the remainder of 2013	590
Projected costs in 2014	1,046
Projected costs in 2015	450
Total future costs	2,086
Capital expenditures for the remainder of 2013	49
Number of ultra-deepwater drill ships under construction	4
Outstanding letters of credit	28.1
Tax benefit recognized		25.4
Number of asbestos related lawsuits	24
Rowan Renaissance [Member]
Status of company's rigs under construction [Abstract]
Scheduled delivery date	Dec. 31, 2013
Total estimated project costs	729
Total costs incurred through June 30, 2013	232
Projected costs for the remainder of 2013	486
Projected costs in 2014	11
Projected costs in 2015	0
Total future costs	497
Rowan Resolute [Member]
Status of company's rigs under construction [Abstract]
Scheduled delivery date	Jun. 30, 2014
Total estimated project costs	737
Total costs incurred through June 30, 2013	261
Projected costs for the remainder of 2013	44
Projected costs in 2014	432
Projected costs in 2015	0
Total future costs	476
Rowan Reliance [Member]
Status of company's rigs under construction [Abstract]
Scheduled delivery date	Oct. 31, 2014
Total estimated project costs	732
Total costs incurred through June 30, 2013	194
Projected costs for the remainder of 2013	34
Projected costs in 2014	500
Projected costs in 2015	4
Total future costs	538
Rowan Relentless [Member]
Status of company's rigs under construction [Abstract]
Scheduled delivery date	Mar. 31, 2015
Total estimated project costs	755
Total costs incurred through June 30, 2013	180
Projected costs for the remainder of 2013	26
Projected costs in 2014	103
Projected costs in 2015	446
Total future costs	$ 575