Retirement Benefits Plans - Benefits Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
United States pension plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 111	$ 123	$ 117
Interest cost	125	156	162
Expected return on plan assets	(250)	(262)	(246)
Amortization	92	119	93
Benefit plans	78	136	126
Settlements, curtailments and other	81	74	71
Total expense	159	210	197
Non-United States pension plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	63	71	66
Interest cost	62	72	85
Expected return on plan assets	(92)	(99)	(98)
Amortization	33	40	27
Benefit plans	66	84	80
Settlements, curtailments and other	3	2	2
Total expense	69	86	82
Other postretirement benefits plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	4	6	13
Interest cost	17	24	32
Expected return on plan assets	(6)	(5)	(6)
Amortization	(9)	2	6
Benefit plans	6	27	45
Settlements, curtailments and other	1	0	(31)
Total expense	$ 7	$ 27	$ 14