Financial instruments and fair value disclosures - Financial instruments measured at fair value (Details) - Recurring - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Liabilities
Long-term debt	$ 2,157	$ 2,556
Liabilities fair value	2,171	2,576
Interest rate swaps
Liabilities
Derivative financial instruments	14	20
Level 2
Liabilities
Long-term debt	2,157	2,556
Liabilities fair value	2,171	2,576
Level 2 \| Interest rate swaps
Liabilities
Derivative financial instruments	$ 14	$ 20

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

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