Debt - Narrative (Details)	6 Months Ended
	Jun. 30, 2015 USD ($)	Jul. 23, 2015 USD ($)	May. 31, 2015 CAD	Apr. 23, 2015 USD ($)	Feb. 28, 2015 EUR (€)	Jan. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Debt instrument, face amount	$ 14,200,000,000						$ 8,400,000,000
Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	6,800,000,000.0
European Medium Term Notes [Member] | Euro Medium Due February 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount | €					€ 650,000,000
Interest rate (percent)					0.85%
Senior Notes [Member] | Floating Rate Senior Notes Due April 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 300,000,000
Parent Company [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				2,400,000,000.0		$ 2,250,000,000.00
Parent Company [Member] | Senior Notes [Member] | Senior Notes Due January 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 1,000,000,000
Interest rate (percent)						3.15%
Parent Company [Member] | Senior Notes [Member] | Senior Notes Due January 2025 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 1,000,000,000
Interest rate (percent)						4.00%
Parent Company [Member] | Senior Notes [Member] | Floating Rate Senior Notes Due January 2020 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 250,000,000
Parent Company [Member] | Senior Notes [Member] | Senior Notes Due April 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 850,000,000
Interest rate (percent)				2.40%
Parent Company [Member] | Senior Notes [Member] | Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 1,250,000,000.00
Interest rate (percent)				3.45%
Parent Company [Member] | Senior Notes [Member] | Notes Due May 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount | CAD			CAD 500,000,000
Interest rate (percent)			3.08%
Parent Company [Member] | Subsequent Event [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 2,300,000,000.0
Parent Company [Member] | Subsequent Event [Member] | Senior Notes [Member] | Senior Notes Due July 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 1,500,000,000.0
Interest rate (percent)		3.20%
Parent Company [Member] | Subsequent Event [Member] | Senior Notes [Member] | Senior Notes Due July 2025 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 800,000,000
Interest rate (percent)		4.30%
Revolving Credit Facility [Member] | Unsecured Debt [Member] | International Segment [Member]
Debt Instrument [Line Items]
Increase in Credit Facilities during period	185,000,000
Revolving Credit Facility [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Increase in Credit Facilities during period	$ 4,100,000,000