Pension and Postretirement Benefit Plans - Components of net periodic benefit cost and other information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
United States Qualified and Non-qualified Pension Benefits
Net periodic benefit cost (benefit)
Service cost	$ 65	$ 73
Interest cost	143	164
Expected return on plan assets	(260)	(267)
Amortization of prior service cost (benefit)	(6)	(6)
Amortization of net actuarial (gain) loss	88	102
Net periodic benefit cost (benefit)	30	66
Net periodic benefit cost (benefit) after settlements, curtailments, special termination benefits and other	30	66
International Qualified and Non-qualified Pension Benefits
Net periodic benefit cost (benefit)
Service cost	33	42
Interest cost	43	55
Expected return on plan assets	(78)	(81)
Amortization of prior service cost (benefit)	(3)	(4)
Amortization of net actuarial (gain) loss	22	38
Net periodic benefit cost (benefit)	17	50
Settlements, curtailments, special terminations and other		(17)
Net periodic benefit cost (benefit) after settlements, curtailments, special termination benefits and other	17	33
Postretirement Benefits
Net periodic benefit cost (benefit)
Service cost	13	21
Interest cost	20	25
Expected return on plan assets	(23)	(22)
Amortization of prior service cost (benefit)	(14)	(8)
Amortization of net actuarial (gain) loss	16	19
Net periodic benefit cost (benefit)	12	35
Net periodic benefit cost (benefit) after settlements, curtailments, special termination benefits and other	$ 12	$ 35