Segment Information - Revenue and Operating Income By Segments (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment									3
Revenue by segment	$ 1,782	$ 1,663	$ 1,593	$ 1,478	$ 1,802	$ 1,677	$ 1,620	$ 1,444	$ 6,516	$ 6,543	$ 6,373
Income from operations	$ 181	$ 200	$ 178	$ 117	$ 146	$ 189	$ 163	$ 101	676	599	135
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue by segment									6,516	6,543	6,373
Operating income by segment									853	840	820
Operating Segments [Member] | Software Segment [Domain]
Segment Reporting Information [Line Items]
Revenue by segment									1,900	1,841	1,747
Operating income by segment									567	577	539
Operating Segments [Member] | Services Segment [Domain]
Segment Reporting Information [Line Items]
Revenue by segment									2,373	2,306	2,218
Operating income by segment									288	201	194
Operating Segments [Member] | Hardware Segment [Domain]
Segment Reporting Information [Line Items]
Revenue by segment									2,243	2,396	2,408
Operating income by segment									(2)	62	87
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other adjustments									177	241	685
Pension mark-to-market adjustments										85	454
Restructuring and other asset-related charges									29	26	74
Acquisition Related Amortization Costs Included in Other Adjustments									115	123	125
Acquisiton Related Costs Included In Other Adjustments									5	7	11
Legal Costs for OFAC and FCPA Investigations									0	0	1
Reserve related to subcontract in Middle East Africa									$ 0	$ 0	$ 20