Revenue Recognition (Deferred Contract Acquisition and Fulfillment Costs) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Deferred Customer Contract Acquisition Costs [Member]
Capitalized Contract Cost, Net [Abstract]
Capitalized Contract Cost, Net (in millions)	$ 5,068		$ 3,974
Capitalized Contract Cost, Amortization (in millions)	1,565	$ 959
Deferred Customer Contract Acquisition Costs [Member] | Other Current Assets [Member]
Capitalized Contract Cost, Net [Abstract]
Capitalized Contract Cost, Net (in millions)	2,190		1,901
Deferred Customer Contract Acquisition Costs [Member] | Other Assets [Member]
Capitalized Contract Cost, Net [Abstract]
Capitalized Contract Cost, Net (in millions)	2,878		2,073
Deferred Customer Contract Fulfillment Cost [Member]
Capitalized Contract Cost, Net [Abstract]
Capitalized Contract Cost, Net (in millions)	11,229		11,540
Capitalized Contract Cost, Amortization (in millions)	3,656	$ 2,983
Deferred Customer Contract Fulfillment Cost [Member] | Other Current Assets [Member]
Capitalized Contract Cost, Net [Abstract]
Capitalized Contract Cost, Net (in millions)	4,589		4,090
Deferred Customer Contract Fulfillment Cost [Member] | Other Assets [Member]
Capitalized Contract Cost, Net [Abstract]
Capitalized Contract Cost, Net (in millions)	$ 6,640		$ 7,450