Property Plant and Equipment Net (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Line Items]
Cost	$ 3,931	$ 3,689
Accumulated amortization	2,429	2,225
Total property and equipment	1,502	1,464
Internal-use software [Member]
Property Plant And Equipment [Line Items]
Cost	2,191	1,942
Accumulated amortization	1,467	1,307
Total property and equipment	724	635
Other property and equipment [Member]
Property Plant And Equipment [Line Items]
Cost	1,740	1,747
Accumulated amortization	962	918
Total property and equipment	778	829
Assets Recorded under Capital Leases [Member]
Property Plant And Equipment [Line Items]
Cost	84	306
Accumulated amortization	36	16
Total property and equipment	$ 48	$ 290