Derivative Financial Instruments - Summary of the impacts of the foreign currency contracts in cash flow hedging relationships (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Loss recognized in OCI on derivatives during the period	$ 0	$ (2)
Loss recognized in OCI on derivatives during the term of the hedging relationship	$ (1)	$ 0

Amount of net unrealized gain (loss) related to the change in fair value of foreign currency exchange rate derivatives designated as cash flow hedging instruments. Recorded in accumulated other comprehensive income to the extent that the cash flow hedge is determined to be effective.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Name:	us-gaap_UnrealizedGainLossOnForeignCurrencyDerivativesNetBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration