Pension and Other Postretirement Employee Benefit Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Dec. 31, 2015
United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 15,900	$ 16,000
Non-U.S. defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,600	$ 3,500
Defined benefit pension plan, non-U.S., expected contribution	47
U.S. non-qualified defined benefit pension plans \| United States
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, non-U.S., expected contribution	33
OPEB plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, non-U.S., expected contribution	$ 2

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 35
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=49178875&loc=d3e12355-114930

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant