Derivatives and Hedging - Earnings and other comprehensive income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flow hedges \| Foreign exchange forward contracts
Derivative instruments
Effective portion of gains and losses included in other comprehensive income	$ (6)	$ (3)	$ (8)
Effective portion of gains and losses reclassified to earnings			(1)
Gains and loss included in earnings	(2)	(1)	(5)
Cash flow hedges \| Interest rate swaps
Derivative instruments
Effective portion of gains and losses included in other comprehensive income	(4)
Derivatives not qualified for hedge accounting \| Foreign exchange forward contracts
Derivative instruments
Gains and loss included in earnings		5	1
Derivatives not qualified for hedge accounting \| Embedded derivatives
Derivative instruments
Gains and loss included in earnings	$ 1	$ (2)	$ (3)

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
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-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

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-Topic 815
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-Name Accounting Standards Codification
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Amount before tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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-Name Accounting Standards Codification
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-Section 45
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