Equity (Share Issuance) (Details) shares in Millions, $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
Sep. 30, 2025 USD ($) shares	Sep. 30, 2025 USD ($) shares	Sep. 30, 2025 USD ($) shares
Equity
Issuance of shares (in shares) \| shares	143.8
Proceeds from issuance of shares, net of issue costs \| $	$ 421		$ 421
Perestroika AS \| Related party
Equity
Issuance of shares (in shares) \| shares	4.0
Proceeds from issuance of shares, net of issue costs \| $	$ 12
Perestroika AS \| Transocean Inc \| Director Affiliated with Perestroika Ltd. \| Related party
Equity
Ownership interest (as a percent)	9.00%	9.00%	9.00%
4.00% Senior Guaranteed Exchangeable Bonds due December 2025
Equity
Shares issued upon conversion (in shares) \| shares		54.7	73.3
Debt issued in exchange transactions \| $		$ 147	$ 196
Debt instrument interest rate stated percentage	4.00%	4.00%	4.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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