Revenue Recognition Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset, Net, Current	$ 3,795	$ 3,486
Contract with Customer, Asset, Net, Noncurrent	1,209	1,142
Contract with Customer, Asset, Net	5,004	4,628
Contract with Customer, Liability, Current	6,107	5,720
Contract with Customer, Liability, Noncurrent	5,166	5,069
Contract with Customer, Liability	11,273	10,789
Contract with Customer, Net	6,269	6,161
Contract with Customer, Liability, Revenue Recognized	2,000
Capitalized Contract Cost, Net	1,072	914
Revenue, Remaining Performance Obligation, Amount	$ 117,500	$ 115,500
Revenue, Remaining Performance Obligations, to be recognized within 24 months	46.00%	46.00%
Contract with Customer, Asset, Change	$ 376
Contract with Customer, Liability, Change	$ 484

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

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Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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