Employee Benefit Plans (Net Periodic Benefit Costs) (Detail) - Pensions - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 48	$ 57
Interest cost	142	196
Amortization of prior service cost	1
Amortization of actuarial losses	(77)
Settlements, curtailments, and special termination benefits	2,354	8
Pensions
Defined Benefit Plan Disclosure [Line Items]
Service cost	48	57	$ 52
Interest cost	142	196	230
Expected return on plan assets	213	287	297
Amortization of prior service cost	(1)	(2)	(2)
Amortization of actuarial losses	110	119	77
Settlements, curtailments, and special termination benefits	1,015	8	8
Net periodic benefit cost	1,101	91	68
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	15	16	15
Interest cost	31	45	47
Expected return on plan assets
Amortization of prior service cost	(31)	(9)	(10)
Amortization of actuarial losses	19	32	11
Net periodic benefit cost	$ 34	$ 84	$ 63