Employee Benefit Plans (Net Periodic Benefit Costs) (Detail) - Pensions - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 59	$ 52
Interest cost	201	230
Amortization of prior service cost	2
Amortization of actuarial losses	(124)
Curtailments and special termination benefits	8	6
Pensions
Defined Benefit Plan Disclosure [Line Items]
Service cost	59	52	$ 57
Interest cost	201	230	218
Expected return on plan assets	295	297	286
Amortization of prior service cost	(2)	(2)	(2)
Amortization of actuarial losses	125	77	102
Curtailments and special termination benefits	8	8	18
Net periodic benefit cost	96	68	107
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	15	20
Interest cost	45	47	$ 49
Expected return on plan assets
Amortization of prior service cost	(9)	(10)	$ (9)
Amortization of actuarial losses	32	11	28
Net periodic benefit cost	$ 85	$ 63	$ 88