Net Periodic Benefit Cost - Continuing Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits, Defined Benefit
Net periodic benefit cost
Service cost	$ 93	$ 128	$ 130
Interest cost	183	211	242
Expected return on plan assets	(298)	(270)	(269)
Amortization of net losses and other deferred amounts	149	192	144
Settlement losses	2	2	1
Net periodic benefit cost	129	220	193
Pension Benefits, Defined Benefit | Discontinued Operations
Net periodic benefit cost
Net periodic benefit cost		(43)	(55)
Other Postretirement Benefit Plans, Defined Benefit
Net periodic benefit cost
Service cost	2	4	5
Interest cost	8	14	25
Amortization of net loss and prior service credit	(19)	(11)	(3)
Curtailment	(4)
Net periodic benefit cost	$ (13)	$ 7	26
Other Postretirement Benefit Plans, Defined Benefit | Discontinued Operations
Net periodic benefit cost
Net periodic benefit cost			$ (1)