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Related Party Transactions - Additional Information (Detail) - USD ($) |  |  |  | 6 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 30, 2018 | Apr. 26, 2017 | Feb. 28, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Nov. 30, 2016 | Mar. 31, 2015
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Investment income, net |  |  |  | $ 19,000,000 | $ 36,000,000 |  |  |  |  |
Seller's credit | $ 565,000,000 |  |  | 565,000,000 |  | $ 547,000,000 |  |  |  |
Debt outstanding | 8,547,000,000 |  |  | 8,547,000,000 |  | 8,701,000,000 |  |  |  |
Secured Debt [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Debt outstanding | 5,476,000,000 |  |  | 5,476,000,000 |  | 5,581,000,000 |  |  |  |
Equity Method Investee [Member] | Medium-term Notes [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Debt, face amount |  |  |  |  |  |  |  |  |  | $ 230,000,000
Archer [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Subordinated loan |  | $ 37,000,000 |  |  |  |  |  |  |  |
Loans payable fair value |  | 56,000,000 |  |  |  |  |  |  |  |
Net gain on debt extinguishment |  | $ 19,000,000 |  |  |  |  |  |  |  |
Fair value of the convertible debt instrument | 58,000,000 |  |  | 58,000,000 |  |  |  |  |  |
Gain on debt component | 2,000,000 |  |  |  |  |  |  |  |  |
Gain on the embedded conversion option | 4,000,000 |  |  |  |  |  |  |  |  |
Private placement |  |  | $ 100,000,000 |  |  |  |  |  |  |
Ownership interest |  | 15.69% |  |  |  |  |  |  |  |
Archer [Member] | Embedded Derivative Option [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Fair value of the convertible debt instrument | 12,000,000 |  |  | 12,000,000 |  |  |  |  |  |
Archer [Member] | Debt [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Fair value of the convertible debt instrument | 46,000,000 |  |  | 46,000,000 |  |  |  |  |  |
Archer [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Notes receivable |  |  |  |  |  |  | $ 37,000,000 |  |  |
Investment income, net |  |  |  | $ 0 | 3,000,000 |  |  |  |  |
Archer [Member] | Equity Method Investee [Member] | Convertible Subordinated Debt [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Due from related parties |  | $ 45,000,000 |  |  |  |  |  |  |  |
Seadrill Jack Up Operations DeMexico [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership |  |  |  | 100.00% |  |  |  |  |  |
Related party expense |  |  |  | $ 1,000,000 | 3,000,000 |  |  |  |  |
SeaMex Limited [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Debt, face amount |  |  |  |  |  |  |  |  |  | 250,000,000
Seller's credit | 250,000,000 |  |  | 250,000,000 |  | 250,000,000 |  |  |  | 250,000,000
Debt outstanding | 250,000,000 |  |  | 250,000,000 |  | 250,000,000 |  |  |  |
Loan to related party | 45,000,000 |  |  | 45,000,000 |  | 45,000,000 |  |  | $ 45,000,000 |
Interest income, related party |  |  |  | $ 12,000,000 | 17,000,000 |  |  |  |  |
Minimum [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Management fee |  |  |  | 4.50% |  |  |  |  |  |
Minimum [Member] | Archer [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  | 16.23% |  |  |  |  |  |  |
Minimum [Member] | Seadrill Jack Up Operations DeMexico [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Management fee |  |  |  | 5.00% |  |  |  |  |  |
Maximum [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Management fee |  |  |  | 8.00% |  |  |  |  |  |
Maximum [Member] | Archer [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  | 39.89% |  |  |  |  |  |  |
Maximum [Member] | Seadrill Jack Up Operations DeMexico [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Management fee |  |  |  | 8.00% |  |  |  |  |  |
LIBOR [Member] | SeaMex Limited [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Loan receivable basis spread on variable rate |  |  |  |  |  |  |  |  | 6.50% |
Revolving Credit Facility [Member] | SeaMex Limited [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Debt, face amount |  |  |  |  |  |  |  |  |  | $ 20,000,000
SeaMex Limited [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Management service agreement termination notice period |  |  |  | 60 days |  |  |  |  |  |
Other revenues |  |  |  | $ 5,000,000 | 5,000,000 |  |  |  |  |
SeaMex Limited [Member] | Drilling Unit [Member] | Equity Method Investee [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Maximum guarantee | 30,000,000 |  |  | 30,000,000 |  | 30,000,000 |  |  |  |
SFL West Vela Limited [Member] | 1.5 Billion Facility [Member] | Secured Debt [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Debt, face amount | 1,500,000,000 |  |  | 1,500,000,000 |  |  |  |  |  |
Sfl West Polaris Limited [Member] | 420 Million Facility [Member] | Secured Debt [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Debt, face amount | 420,000,000 |  |  | 420,000,000 |  |  |  |  |  |
Performance Guarantee [Member] | Seadrill Partners LLC [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Guarantees | 57,000,000 |  |  | 57,000,000 |  | 165,000,000 |  |  |  |
Financial Guarantee [Member] | Seadrill Partners LLC [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Guarantees |  |  |  |  |  | 0 |  |  |  |
Financial Guarantee [Member] | Archer [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Guarantees |  |  |  |  | $ 278,000,000 |  | 278,000,000 |  |  |
Subordinated loan |  |  |  |  |  |  | $ 149,000,000 |  |  |
Contingent liability recognized |  |  |  |  |  |  |  | $ 28,000,000 |  |
Custom Guarantee [Member] | Seadrill Partners LLC [Member] |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Guarantees | $ 0 |  |  | $ 0 |  | $ 600,000 |  |  |  |

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