Retirement Benefits (Details 9) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	$ 25,592	$ 25,103
Derivatives, notional amount	147	141
Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	2,549	1,494
U.S. Equity Securities [Member]
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	3,689	4,045
Alternative Investments, Fair Value Disclosure	700	593
International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	2,441	2,381
Alternative Investments, Fair Value Disclosure	3,329	2,470
U.S. Treasuries
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	1,109	530
U.S. Government Agency
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	424	717
Non-U.S. Government
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	108	274
Corporate debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	3,723	4,876
Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	297	393
High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	1,844	1,678
Bank loans
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	297	261
Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	2	25
Fixed Income Funds
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Alternative Investments, Fair Value Disclosure	99	133
Hedge Funds
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Alternative Investments, Fair Value Disclosure	220	219
OpportunisticFunds
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Alternative Investments, Fair Value Disclosure	581	278
Private Equity Funds [Member]
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Alternative Investments, Fair Value Disclosure	1,801	1,850
Real Estate [Member]
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Alternative Investments, Fair Value Disclosure	2,379	2,886
Level 1
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	6,140	6,400
Level 1 | Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	72	37
Level 1 | U.S. Equity Securities [Member]
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	3,686	4,043
Level 1 | International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	2,392	2,300
Level 1 | Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	(10)	20
Level 2
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	10,338	10,271
Level 2 | Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	2,477	1,457
Level 2 | U.S. Equity Securities [Member]
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	0	0
Level 2 | International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	48	81
Level 2 | U.S. Treasuries
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	1,109	530
Level 2 | U.S. Government Agency
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	424	717
Level 2 | Non-U.S. Government
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	108	274
Level 2 | Corporate debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	3,723	4,876
Level 2 | Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	296	392
Level 2 | High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	1,844	1,678
Level 2 | Bank loans
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	297	261
Level 2 | Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	12	5
Level 3
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	5	3
Level 3 | U.S. Equity Securities [Member]
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	3	2
Level 3 | International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	1
Level 3 | Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets	1	1
Pension and Other Post-retirement benefit plans [Member]
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Derivative Asset	19	40
Derivative Liability	(28)	(25)
Derivatives, notional amount	$ 2,000	$ 3,200