Benefit Plans - Amounts Recognized in the Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits [Member]
Amounts recognized in the Consolidated Balance Sheets consist of:
Other assets	$ 5	$ 9
Other liabilities	(566)	(624)
Net amount recognized	(561)	(615)
Other Postretirement Benefits [Member]
Amounts recognized in the Consolidated Balance Sheets consist of:
Other assets	54	49
Other liabilities	(16)	(17)
Net amount recognized	$ 38	$ 32