Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 27, 2020
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
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
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		615,110,302
Entity Central Index Key	0001451505
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Shares
Document and Entity Information
Title of 12(b) Security	Shares
Trading Symbol	RIG
Security Exchange Name	NYSE
0.50% Exchangeable Senior Bonds due January 2023
Document and Entity Information
Title of 12(b) Security	0.50% Exchangeable Senior Bonds due 2023
Trading Symbol	RIG/23
Security Exchange Name	NYSE