Segment Reporting - Revenue and Long-lived Assets by Geography (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total Revenues	[1]	$ 18,045	$ 19,540	$ 20,006
Long-Lived Assets	[2]	1,989	2,630	2,874
United States
Segment Reporting Information [Line Items]
Total Revenues		12,557	13,041	13,272
Long-Lived Assets	[2]	1,279	1,758	1,870
Europe
Segment Reporting Information [Line Items]
Total Revenues		3,783	4,428	4,414
Long-Lived Assets	[2]	476	632	761
Other areas
Segment Reporting Information [Line Items]
Total Revenues		1,705	2,071	2,320
Long-Lived Assets	[2]	$ 234	$ 240	$ 243

[1] Asset information on a segment basis is not disclosed as this information is not separately identified and internally reported to our Chief Operating Decision Maker (CODM).

[2] Long-lived assets are comprised of (i) Land, buildings and equipment, net, (ii) Equipment on operating leases, net, (iii) Internal use software, net and (iv) Product software, net.