Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue recognized which was included in the contract liability balance	$ 170
Capitalized contract costs, amortization	24
Retained Earnings | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment of ASU adoption			$ 208
Product
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of consolidated revenue (less than)		4.00%
Sales Commissions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract costs	312
Conversion or Implementation Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract costs	$ 89
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining revenue performance obligation, optional exemption, contract term	3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining revenue performance obligation, optional exemption, contract term	5 years