Fair Value Measurements (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average pay rate for the Company's interest rate swap agreements (in hundredths)	1.61%		1.61%		1.87%
Carrying Value	$ 33,281		$ 33,281		$ 21,023
Asset Impairment Charges	0	$ 0	0	$ 0
Senior notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	26,036		26,036		13,831
Credit facilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	7,245		7,245		7,192
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Funds	11,692		11,692		4,112
Commercial Paper	0		0		0
Fair value of interest rate derivatives not designated as hedges	0		0		0
Fair Value, Inputs, Level 1 [Member] | Senior notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	25,653		25,653		14,205
Fair Value, Inputs, Level 1 [Member] | Credit facilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	7,217		7,217		7,186
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Funds	0		0		0
Commercial Paper	7,934		7,934		2,999
Fair value of interest rate derivatives not designated as hedges	21		21		18
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Funds	0		0		0
Commercial Paper	0		0		0
Fair value of interest rate derivatives not designated as hedges	$ 0		$ 0		$ 0