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Revenue Recognition - Narrative (Details)
$ in Millions
3 Months Ended
Jan. 01, 2018
USD ($)
Mar. 31, 2018
USD ($)
country
Rate
Dec. 31, 2017
USD ($)
Disaggregation of Revenue [Line Items]      
Percentage of Service Revenue Recognize over Time | Rate   0.00%  
Number of countries in which entity operates | country   85  
Contract liabilities     $ 251
Revenue, remaining performance obligation   $ 125  
Accounting Standards Update 2014-09 [Member]      
Disaggregation of Revenue [Line Items]      
Cumulative effect on retained earnings, net of tax $ 64