Derivative instruments - Contracts Falling under Early Termination Provisions (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Credit Derivatives [Line Items]
Aggregate fair value of OTC derivatives in net liability positions	$ 3,442	$ 2,877
Collateral posted	3,671	2,801
A3 \| A-
Credit Derivatives [Line Items]
Aggregate fair value of OTC derivatives in net liability positions	56	15
Baa2 \| BBB
Credit Derivatives [Line Items]
Aggregate fair value of OTC derivatives in net liability positions	608	116
Ba1 \| BB plus
Credit Derivatives [Line Items]
Aggregate fair value of OTC derivatives in net liability positions	$ 2,084	$ 1,041

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959

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- Definition

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.

+ References

No definition available.

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- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959

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