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Other Financial Data - Accounts Receivable, Net, Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in accounts receivable	$ (1,159)	$ (1,198)	$ (1,523)
Contract assets	760	931	$ 0
Avigilon and Plant Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Receivables acquired	87
Restatement Adjustment \| Adjustments due to ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in accounts receivable		24
Contract assets		$ 0
Other Receivables \| Restatement Adjustment \| Adjustments due to ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in accounts receivable	24
Contract assets	24
Unbilled Receivables \| Restatement Adjustment \| Adjustments due to ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in accounts receivable	297
Contract assets	$ 297