Retirement-Related Benefits - All Retirement Plans Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Retirement-Related Benefits:
Defined benefit and contribution pension plans - cost	$ 421	$ 505	$ 1,315	$ 1,747
Nonpension postretirement plans - cost	64	68	185	206
Total	$ 486	$ 573	$ 1,500	$ 1,953
Year-to-year percent change, defined benefit and contribution pension plans cost (as a percent)	(16.60%)		(24.70%)
Year-to-year percent change, nonpension postretirement plans cost (as a percent)	(4.80%)		(10.30%)
Year-to-year percent change, total (as a percent)	(15.20%)		(23.20%)