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Postemployment Benefit Plans (Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair value of plan assets
Total investments	$ 1,799	$ 1,567	$ 1,736
Funding contributions
Employer contributions	22	$ 17	15
Projected pension benefits payments
2020	90
2021	90
2022	92
2023	93
2024	95
2025-2029	$ 481
U.S.
Weighted-average target allocations of the investments
Total target allocation percentage	100.00%	100.00%
Total actual allocation percentage	100.00%	100.00%
U.S. \| Equity securities
Weighted-average target allocations of the investments
Total target allocation percentage	50.00%	50.00%
Total actual allocation percentage	51.00%	50.00%
U.S. \| Fixed income securities
Weighted-average target allocations of the investments
Total target allocation percentage	50.00%	50.00%
Total actual allocation percentage	49.00%	50.00%
Non-U.S. Plans
Weighted-average target allocations of the investments
Total target allocation percentage	100.00%	100.00%
Total actual allocation percentage	100.00%	100.00%
Non-U.S. Plans \| Equity securities
Weighted-average target allocations of the investments
Total target allocation percentage	24.00%	34.00%
Total actual allocation percentage	27.00%	32.00%
Non-U.S. Plans \| Fixed income securities
Weighted-average target allocations of the investments
Total target allocation percentage	60.00%	51.00%
Total actual allocation percentage	56.00%	52.00%
Non-U.S. Plans \| Other investments
Weighted-average target allocations of the investments
Total target allocation percentage	16.00%	15.00%
Total actual allocation percentage	17.00%	16.00%
Transocean Plans
Fair value of plan assets
Total investments	$ 1,799	$ 1,567
Funding contributions
Expected defined plan contributions next year	18
Transocean Plans \| Significant observable inputs
Fair value of plan assets
Total investments	1,361	1,178
Transocean Plans \| Significant other observable inputs
Fair value of plan assets
Total investments	438	389
Transocean Plans \| Mutual funds
Fair value of plan assets
Total investments	1,719	1,498
Transocean Plans \| Mutual funds \| Significant observable inputs
Fair value of plan assets
Total investments	1,352	1,171
Transocean Plans \| Mutual funds \| Significant other observable inputs
Fair value of plan assets
Total investments	367	327
Transocean Plans \| U.S. equity funds
Fair value of plan assets
Total investments	481	401
Transocean Plans \| U.S. equity funds \| Significant observable inputs
Fair value of plan assets
Total investments	480	401
Transocean Plans \| U.S. equity funds \| Significant other observable inputs
Fair value of plan assets
Total investments	1
Transocean Plans \| Non-U.S. equity funds
Fair value of plan assets
Total investments	336	304
Transocean Plans \| Non-U.S. equity funds \| Significant observable inputs
Fair value of plan assets
Total investments	216	179
Transocean Plans \| Non-U.S. equity funds \| Significant other observable inputs
Fair value of plan assets
Total investments	120	125
Transocean Plans \| Bond funds
Fair value of plan assets
Total investments	902	793
Transocean Plans \| Bond funds \| Significant observable inputs
Fair value of plan assets
Total investments	656	591
Transocean Plans \| Bond funds \| Significant other observable inputs
Fair value of plan assets
Total investments	246	202
Transocean Plans \| Other investments
Fair value of plan assets
Total investments	80	69
Transocean Plans \| Other investments \| Significant observable inputs
Fair value of plan assets
Total investments	9	7
Transocean Plans \| Other investments \| Significant other observable inputs
Fair value of plan assets
Total investments	71	62
Transocean Plans \| Cash and money market funds
Fair value of plan assets
Total investments	9	7
Transocean Plans \| Cash and money market funds \| Significant observable inputs
Fair value of plan assets
Total investments	9	7
Transocean Plans \| Property collective trusts
Fair value of plan assets
Total investments	20	19
Transocean Plans \| Property collective trusts \| Significant other observable inputs
Fair value of plan assets
Total investments	20	19
Transocean Plans \| Investment contracts
Fair value of plan assets
Total investments	51	43
Transocean Plans \| Investment contracts \| Significant other observable inputs
Fair value of plan assets
Total investments	51	43
Transocean Plans \| U.S.
Fair value of plan assets
Total investments	1,369	1,189	1,343
Funding contributions
Employer contributions	4	2
Projected pension benefits payments
2020	79
2021	79
2022	81
2023	82
2024	82
2025-2029	419
Transocean Plans \| U.S. \| Significant observable inputs
Fair value of plan assets
Total investments	1,357	1,177
Transocean Plans \| U.S. \| Significant other observable inputs
Fair value of plan assets
Total investments	12	12
Transocean Plans \| U.S. \| Mutual funds
Fair value of plan assets
Total investments	1,364	1,183
Transocean Plans \| U.S. \| Mutual funds \| Significant observable inputs
Fair value of plan assets
Total investments	1,352	1,171
Transocean Plans \| U.S. \| Mutual funds \| Significant other observable inputs
Fair value of plan assets
Total investments	12	12
Transocean Plans \| U.S. \| U.S. equity funds
Fair value of plan assets
Total investments	481	401
Transocean Plans \| U.S. \| U.S. equity funds \| Significant observable inputs
Fair value of plan assets
Total investments	480	401
Transocean Plans \| U.S. \| U.S. equity funds \| Significant other observable inputs
Fair value of plan assets
Total investments	1
Transocean Plans \| U.S. \| Non-U.S. equity funds
Fair value of plan assets
Total investments	221	184
Transocean Plans \| U.S. \| Non-U.S. equity funds \| Significant observable inputs
Fair value of plan assets
Total investments	216	179
Transocean Plans \| U.S. \| Non-U.S. equity funds \| Significant other observable inputs
Fair value of plan assets
Total investments	5	5
Transocean Plans \| U.S. \| Bond funds
Fair value of plan assets
Total investments	662	598
Transocean Plans \| U.S. \| Bond funds \| Significant observable inputs
Fair value of plan assets
Total investments	656	591
Transocean Plans \| U.S. \| Bond funds \| Significant other observable inputs
Fair value of plan assets
Total investments	6	7
Transocean Plans \| U.S. \| Other investments
Fair value of plan assets
Total investments	5	6
Transocean Plans \| U.S. \| Other investments \| Significant observable inputs
Fair value of plan assets
Total investments	5	6
Transocean Plans \| U.S. \| Cash and money market funds
Fair value of plan assets
Total investments	5	6
Transocean Plans \| U.S. \| Cash and money market funds \| Significant observable inputs
Fair value of plan assets
Total investments	5	6
Transocean Plans \| Non-U.S. Plans
Fair value of plan assets
Total investments	430	378	$ 393
Funding contributions
Employer contributions	16	13
Projected pension benefits payments
2020	8
2021	8
2022	8
2023	9
2024	10
2025-2029	59
Transocean Plans \| Non-U.S. Plans \| Significant observable inputs
Fair value of plan assets
Total investments	4	1
Transocean Plans \| Non-U.S. Plans \| Significant other observable inputs
Fair value of plan assets
Total investments	426	377
Transocean Plans \| Non-U.S. Plans \| Mutual funds
Fair value of plan assets
Total investments	355	315
Transocean Plans \| Non-U.S. Plans \| Mutual funds \| Significant other observable inputs
Fair value of plan assets
Total investments	355	315
Transocean Plans \| Non-U.S. Plans \| Non-U.S. equity funds
Fair value of plan assets
Total investments	115	120
Transocean Plans \| Non-U.S. Plans \| Non-U.S. equity funds \| Significant other observable inputs
Fair value of plan assets
Total investments	115	120
Transocean Plans \| Non-U.S. Plans \| Bond funds
Fair value of plan assets
Total investments	240	195
Transocean Plans \| Non-U.S. Plans \| Bond funds \| Significant other observable inputs
Fair value of plan assets
Total investments	240	195
Transocean Plans \| Non-U.S. Plans \| Other investments
Fair value of plan assets
Total investments	75	63
Transocean Plans \| Non-U.S. Plans \| Other investments \| Significant observable inputs
Fair value of plan assets
Total investments	4	1
Transocean Plans \| Non-U.S. Plans \| Other investments \| Significant other observable inputs
Fair value of plan assets
Total investments	71	62
Transocean Plans \| Non-U.S. Plans \| Cash and money market funds
Fair value of plan assets
Total investments	4	1
Transocean Plans \| Non-U.S. Plans \| Cash and money market funds \| Significant observable inputs
Fair value of plan assets
Total investments	4	1
Transocean Plans \| Non-U.S. Plans \| Property collective trusts
Fair value of plan assets
Total investments	20	19
Transocean Plans \| Non-U.S. Plans \| Property collective trusts \| Significant other observable inputs
Fair value of plan assets
Total investments	20	19
Transocean Plans \| Non-U.S. Plans \| Investment contracts
Fair value of plan assets
Total investments	51	43
Transocean Plans \| Non-U.S. Plans \| Investment contracts \| Significant other observable inputs
Fair value of plan assets
Total investments	51	43
OPEB Plans
Funding contributions
Employer contributions	2	$ 2
Expected defined plan contributions next year	3
Projected pension benefits payments
2020	3
2021	3
2022	3
2023	2
2024	3
2025-2029	$ 3