Derivative Financial Instruments - Schedule of Notional Amounts of Outstanding Derivative Positions (Details) - Derivatives designated as hedges € in Millions, £ in Millions, CAD in Millions, AUD in Millions, $ in Millions	Jun. 30, 2017 USD ($)	Jun. 30, 2017 GBP (£)	Jun. 30, 2017 EUR (€)	Jun. 30, 2017 AUD	Jun. 30, 2017 CAD	Jun. 14, 2017 EUR (€)	Jan. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 GBP (£)	Dec. 31, 2016 EUR (€)	Dec. 31, 2016 AUD	Dec. 31, 2016 CAD
Derivatives, Fair Value [Line Items]
Assets	$ 34							$ 147
Liabilities	(22)							0
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Assets	31							144
Liabilities	(22)							0
Foreign exchange contracts | AUD
Derivatives, Fair Value [Line Items]
Notional Value | AUD				AUD 100							AUD 211
Assets	29							57
Liabilities	0							0
Foreign exchange contracts | EUR
Derivatives, Fair Value [Line Items]
Notional Value | €			€ 915			€ 915				€ 0
Assets	0							0
Liabilities	(22)							0
Foreign exchange contracts | GBP
Derivatives, Fair Value [Line Items]
Notional Value | £		£ 150							£ 300
Assets	1							78
Liabilities	0							0
Foreign exchange contracts | CAD
Derivatives, Fair Value [Line Items]
Notional Value | CAD					CAD 95							CAD 130
Assets	1							9
Liabilities	0							0
Interest rate collar contracts
Derivatives, Fair Value [Line Items]
Notional Value							$ 1,300
Interest rate collar contracts | USD
Derivatives, Fair Value [Line Items]
Notional Value	4,300							3,000
Assets	3							3
Liabilities	$ 0							$ 0