Revenue from Contracts with Customers - Disaggregation of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 526	$ 526	$ 1,576	$ 1,530
United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	277	292	828	830
Non-US
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	249	234	748	700
Subscriptions Revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	312	292	926	846
Subscriptions Revenue | United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	200	188	591	549
Subscriptions Revenue | Non-US
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	113	104	335	297
Software and Hardware Perpetual Revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	77	90	243	271
Software and Hardware Perpetual Revenue | United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	29	50	92	118
Software and Hardware Perpetual Revenue | Non-US
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	47	41	151	154
Consulting Revenue | United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	48	54	145	163
Consulting Revenue | Non-US
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 89	$ 89	$ 262	$ 249