Accumulated Other Comprehensive Loss (Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	$ 9
Tax benefit (cost) related to unrealized currency translation adjustments other than translation of foreign denominated balance sheets	4	$ 141	$ (34)
Tax benefit (cost) related to the adjustment for pension and other postretirement benefits	(34)	(33)	(403)
Cumulative tax benefit related to the adjustment for pension and other postretirement benefits	209	243
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	$ 2	$ 5	$ 2