Goodwill and Other Intangible Assets - Schedule of other intangible assets by asset class (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives, gross carrying amount	$ 4,542	$ 4,323
Intangible assets with finite lives, accumulated amortization	2,022	1,745
Intangible assets, net	2,520	2,578
Amortization expense on intangible assets	352	395	423
Tradenames [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives, gross carrying amount	1,019	1,019
Intangible assets with finite lives, accumulated amortization	0	0
Intangible assets, net	1,019	1,019
Customer related and contract based [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives, gross carrying amount	2,952	2,720
Intangible assets with finite lives, accumulated amortization	1,579	1,310
Intangible assets, net	1,373	1,410
Technology and other [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives, gross carrying amount	571	584
Intangible assets with finite lives, accumulated amortization	443	435
Intangible assets, net	$ 128	$ 149