Document and Entity Information - shares
6 Months Ended
Jun. 30, 2019
Jul. 23, 2019
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2019  
Document Transition Report false  
Entity File Number 001-38373  
Entity Registrant Name Transocean Ltd  
Entity Incorporation, State or Country Code V8  
Entity Tax Identification Number 98-0599916  
Entity Address, Address Line One Turmstrasse 30  
Entity Address, City or Town Steinhausen  
Entity Address, Country CH  
Entity Address, Postal Zip Code 6312  
City Area Code +41 (41)  
Local Phone Number 749-0500  
Title of 12(b) Security Shares  
Trading Symbol RIG  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   611,803,445
Entity Central Index Key 0001451505  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Amendment Flag false