Debt - Key Components of Long-term Debt (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Carrying Value	$ 5,479,000,000	$ 5,479,000,000	$ 5,475,000,000
Long-term Notes $2.5B
Debt Instrument [Line Items]
Debt, face amount	$ 2,500,000,000	$ 2,500,000,000
Stated interest rate	1.875%	1.875%
Issued at Discount to Par		99.943%
Carrying Value	$ 2,499,000,000	$ 2,499,000,000
Long-term Notes $2.0B
Debt Instrument [Line Items]
Debt, face amount	$ 2,000,000,000	$ 2,000,000,000
Stated interest rate	2.65%	2.65%
Issued at Discount to Par		99.76%
Carrying Value	$ 1,997,000,000	$ 1,997,000,000
Long-term Notes $1.0B
Debt Instrument [Line Items]
Debt, face amount	$ 1,000,000,000	$ 1,000,000,000
Stated interest rate	3.375%	3.375%
Issued at Discount to Par		99.925%
Carrying Value	$ 1,000,000,000	$ 1,000,000,000
Long-term Notes $5.5B
Debt Instrument [Line Items]
Carrying Value	$ 5,496,000,000	5,496,000,000
Debt Issuance Cost		$ (17,000,000)
Long-term Debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	2.55%	2.55%