Retirement-Related Benefits - All Retirement Plans Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Retirement-Related Benefits:
Defined benefit and contribution pension plans - cost	$ 455	$ 493	$ 894	$ 1,242
Nonpension postretirement plans - cost	61	67	121	139
Total	$ 516	$ 560	$ 1,014	$ 1,380
Year-to-year percent change, defined benefit and contribution pension plans cost (as a percent)	(7.70%)		(28.00%)
Year-to-year percent change, nonpension postretirement plans cost (as a percent)	(9.80%)		(13.00%)
Year-to-year percent change, total (as a percent)	(7.90%)		(26.50%)