Fair Value Measurements and Financial Instruments Schedule of assets and liabilities that are measured at fair value on a recurring basis (Details) (Recurring [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Fair Value [Member] | Money market funds and highly liquid debt securities
Assets:
Money market funds and highly liquid debt securities	$ 1,787	[1]	$ 1,850	[2]
Fair Value [Member] | Money market funds [Member]
Assets:
Money market funds and highly liquid debt securities	1,787		1,850
Fair Value [Member] | Corporate bonds [Member]
Assets:
Other investments	1		1
Fair Value [Member] | Government bonds [Member]
Assets:
Other investments	6		6
Fair Value [Member] | Equity investments [Member]
Assets:
Other investments	10		11
Fair Value [Member] | Interest rate contracts [Member]
Assets:
Derivatives	0		0
Fair Value [Member] | Foreign exchange contracts [Member]
Assets:
Derivatives	59		46
Liabilities:
Derivatives	79		58
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money market funds and highly liquid debt securities
Assets:
Money market funds and highly liquid debt securities	1,787	[1]	1,850	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate bonds [Member]
Assets:
Other investments	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Government bonds [Member]
Assets:
Other investments	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity investments [Member]
Assets:
Other investments	6		6
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Interest rate contracts [Member]
Assets:
Derivatives	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign exchange contracts [Member]
Assets:
Derivatives	0		0
Liabilities:
Derivatives	0		0
Significant Other Observable Inputs (Level 2) [Member] | Money market funds and highly liquid debt securities
Assets:
Money market funds and highly liquid debt securities	0	[1]	0	[2]
Significant Other Observable Inputs (Level 2) [Member] | Corporate bonds [Member]
Assets:
Other investments	0		0
Significant Other Observable Inputs (Level 2) [Member] | Government bonds [Member]
Assets:
Other investments	6		6
Significant Other Observable Inputs (Level 2) [Member] | Equity investments [Member]
Assets:
Other investments	4		5
Significant Other Observable Inputs (Level 2) [Member] | Interest rate contracts [Member]
Assets:
Derivatives	0		0
Significant Other Observable Inputs (Level 2) [Member] | Foreign exchange contracts [Member]
Assets:
Derivatives	59		46
Liabilities:
Derivatives	79		58
Significant Unobservable Inputs (Level 3) [Member] | Money market funds and highly liquid debt securities
Assets:
Money market funds and highly liquid debt securities	0	[1]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Corporate bonds [Member]
Assets:
Other investments	1		1
Significant Unobservable Inputs (Level 3) [Member] | Government bonds [Member]
Assets:
Other investments	0		0
Significant Unobservable Inputs (Level 3) [Member] | Equity investments [Member]
Assets:
Other investments	0		0
Significant Unobservable Inputs (Level 3) [Member] | Interest rate contracts [Member]
Assets:
Derivatives	0		0
Significant Unobservable Inputs (Level 3) [Member] | Foreign exchange contracts [Member]
Assets:
Derivatives	0		0
Liabilities:
Derivatives	$ 0		$ 0

[1] Includes $1,787 million of money market funds that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity.

[2] Includes $1,850 million of money market funds that are classified as Fiduciary assets, Short-term investments or Cash and cash equivalents in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity.