Property, Plant, and Capitalized Software Property Plant and Equipment Table (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Land and improvements	$ 405	$ 324
Buildings and improvements	3,664	3,148
Computer equipment	1,829	2,021
Furniture and fixtures	1,208	999
Less accumulated depreciation	(2,488)	(2,621)
Property and equipment, net	4,618	3,871
Capitalized software	3,601	3,158
Less accumulated amortization	(1,206)	(1,128)
Capitalized software, net	2,395	2,030
Total property, equipment and capitalized software, net	$ 7,013	$ 5,901