Postemployment Benefit Plans (Assumptions) (Details) - plan	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
U.S. | Funded Plan
Postemployment Benefit Plans
Number of benefit plans	3
U.S. | Unfunded Plan
Postemployment Benefit Plans
Number of benefit plans	3
U.K. | Funded Plan
Postemployment Benefit Plans
Number of benefit plans	1
Norway | Funded Plan
Postemployment Benefit Plans
Number of benefit plans	4
Norway | Unfunded Plan
Postemployment Benefit Plans
Number of benefit plans	2
Transocean Plans | U.S.
Weighted average assumptions used to determine benefit obligations
Discount rate (as a percent)	3.27%	4.31%
Weighted-average assumptions used to determine net periodic benefit costs
Discount rate (as a percent)	4.32%	3.68%	4.26%
Expected rate of return (as a percent)	6.20%	6.21%	6.31%
Transocean Plans | Non-U.S. Plans
Weighted average assumptions used to determine benefit obligations
Discount rate (as a percent)	2.13%	2.86%
Compensation trend rate (as a percent)	2.25%	2.75%
Weighted-average assumptions used to determine net periodic benefit costs
Discount rate (as a percent)	2.86%	2.49%	2.69%
Expected rate of return (as a percent)	4.39%	4.72%	4.79%
Compensation trend rate (as a percent)	2.75%	2.50%	2.25%
OPEB Plans
Weighted average assumptions used to determine benefit obligations
Discount rate (as a percent)	2.39%	3.56%
Weighted-average assumptions used to determine net periodic benefit costs
Discount rate (as a percent)	3.56%	2.93%	3.08%