Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 11, 2020	Jan. 17, 2020
Principal amount
Debt due within one year	$ 448	$ 449
Long-term debt	6,372	6,927
Carrying amount
Total debt	7,170	7,807
Debt due within one year	513	505
Long-term debt	$ 6,657	7,302
Transocean Inc
Carrying amount
Percentage ownership interest in Transocean Inc. by Transocean Ltd.	100.00%
6.375% Senior Notes due December 2021
Principal amount
Total installments of debt		38
Carrying amount
Total debt		38
Debt due within one year		38
Debt instrument interest rate stated percentage	6.375%
5.52% Senior Secured Notes due May 2022
Principal amount
Total installments of debt	$ 18	111
Debt due within one year	18	93
Carrying amount
Total debt	18	111
Debt due within one year	$ 18	92
Debt instrument interest rate stated percentage	5.52%
3.80% Senior Notes due October 2022
Principal amount
Total installments of debt	$ 27	27
Debt due within one year	27
Carrying amount
Total debt	27	27
Debt due within one year	$ 27
Debt instrument interest rate stated percentage	3.80%
Interest rate, as adjusted (as a percent)	5.80%
0.50% Exchangeable Senior Bonds due January 2023
Principal amount
Total installments of debt	$ 140	463
Carrying amount
Total debt	$ 140	462
Debt instrument interest rate stated percentage	0.50%
5.375% Senior Secured Notes due May 2023
Principal amount
Total installments of debt	$ 306	364
Debt due within one year	63	47
Carrying amount
Total debt	304	360
Debt due within one year	$ 62	46
Debt instrument interest rate stated percentage	5.375%
5.875% Senior Secured Notes due January 2024
Principal amount
Total installments of debt	$ 435	585
Debt due within one year	83	83
Carrying amount
Total debt	430	577
Debt due within one year	$ 80	80
Debt instrument interest rate stated percentage	5.875%
7.75% Senior Secured Notes due October 2024
Principal amount
Total installments of debt	$ 300	360
Debt due within one year	60	60
Carrying amount
Total debt	296	354
Debt due within one year	$ 58	58
Debt instrument interest rate stated percentage	7.75%
6.25% Senior Secured Notes due December 2024
Principal amount
Total installments of debt	$ 313	375
Debt due within one year	62	62
Carrying amount
Total debt	309	369
Debt due within one year	$ 61	60
Debt instrument interest rate stated percentage	6.25%
6.125% Senior Secured Notes due August 2025
Principal amount
Total installments of debt	$ 402	468
Debt due within one year	66	66
Carrying amount
Total debt	397	461
Debt due within one year	$ 64	64
Debt instrument interest rate stated percentage	6.125%
7.25% Senior Notes due November 2025
Principal amount
Total installments of debt	$ 411	411
Carrying amount
Total debt	$ 406	405
Debt instrument interest rate stated percentage	7.25%
4.00% Senior Guaranteed Exchangeable Bonds due December 2025
Principal amount
Total installments of debt	$ 294
Carrying amount
Total debt	$ 264
Debt instrument interest rate stated percentage	4.00%
7.50% Senior Notes due January 2026
Principal amount
Total installments of debt	$ 569	569
Carrying amount
Total debt	$ 565	565
Debt instrument interest rate stated percentage	7.50%
2.50% Senior Guaranteed Exchangeable Bonds due January 2027
Principal amount
Total installments of debt	$ 238	238
Carrying amount
Total debt	271	277
Debt due within one year	$ 6	6
Debt instrument interest rate stated percentage	2.50%
2.50% Senior Guaranteed Exchangeable Bonds due January 2027 | Perestroika AS
Principal amount
Total installments of debt	$ 213	213
11.50% Senior Guaranteed Notes due January 2027
Principal amount
Total installments of debt	687	687
Carrying amount
Total debt	1,078	1,139
Debt due within one year	$ 70	61
Debt instrument interest rate stated percentage	11.50%		11.50%
6.875% Senior Secured Notes due February 2027
Principal amount
Total installments of debt	$ 550	550
Debt due within one year	69
Carrying amount
Total debt	544	542
Debt due within one year	$ 67
Debt instrument interest rate stated percentage	6.875%
8.00% Senior Notes due February 2027
Principal amount
Total installments of debt	$ 612	612
Carrying amount
Total debt	$ 607	606
Debt instrument interest rate stated percentage	8.00%			8.00%
7.45% Notes due April 2027
Principal amount
Total installments of debt	$ 52	52
Carrying amount
Total debt	$ 52	51
Debt instrument interest rate stated percentage	7.45%
8.00% Debentures due April 2027
Principal amount
Total installments of debt	$ 22	22
Carrying amount
Total debt	$ 22	22
Debt instrument interest rate stated percentage	8.00%
7.00% Notes due June 2028
Principal amount
Total installments of debt	$ 261	261
Carrying amount
Total debt	$ 265	266
Debt instrument interest rate stated percentage	7.00%
7.50% Notes due April 2031
Principal amount
Total installments of debt	$ 396	396
Carrying amount
Total debt	$ 394	394
Debt instrument interest rate stated percentage	7.50%
6.80% Senior Notes due March 2038
Principal amount
Total installments of debt	$ 610	610
Carrying amount
Total debt	$ 605	605
Debt instrument interest rate stated percentage	6.80%
7.35% Senior Notes due December 2041
Principal amount
Total installments of debt	$ 177	177
Carrying amount
Total debt	$ 176	176
Debt instrument interest rate stated percentage	7.35%
Interest rate, as adjusted (as a percent)	9.35%
Principal installments
Principal amount
Total installments of debt	$ 6,820	$ 7,376