Debt - Key Components of Long-term Debt (Details) - USD ($)	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Carrying Value	$ 5,474,000,000	$ 5,469,000,000
Long-term Notes $2.5B
Debt Instrument [Line Items]
Debt, face amount	$ 2,500,000,000
Stated interest rate	1.875%
Issued at Discount to Par	99.943%
Carrying Value	$ 2,499,000,000
Long-term Notes $2.0B
Debt Instrument [Line Items]
Debt, face amount	$ 2,000,000,000
Stated interest rate	2.65%
Issued at Discount to Par	99.76%
Carrying Value	$ 1,996,000,000
Long-term Notes $1.0B
Debt Instrument [Line Items]
Debt, face amount	$ 1,000,000,000
Stated interest rate	3.375%
Issued at Discount to Par	99.925%
Carrying Value	$ 1,000,000,000
Long-term Notes $5.5B
Debt Instrument [Line Items]
Carrying Value	5,495,000,000
Debt Issuance Cost	$ (21,000,000)