Segment Information - Schedule of consolidated non-current assets by geographic area (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets, net	$ 765	$ 765
Goodwill, intangible assets and other	12,382	12,253
Total	13,147	13,018
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets, net	443	432
Goodwill, intangible assets and other	6,947	6,635
Total	7,390	7,067
Americas other than U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets, net	62	48
Goodwill, intangible assets and other	887	368
Total	949	416
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets, net	65	89
Goodwill, intangible assets and other	2,091	2,606
Total	2,156	2,695
Europe, Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets, net	85	89
Goodwill, intangible assets and other	2,054	2,181
Total	2,139	2,270
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed assets, net	110	107
Goodwill, intangible assets and other	403	463
Total	$ 513	$ 570