Segments (Results of Operations and Average Assets by Segment) (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information
Impairment of Branches and Land	$ 45	$ 7	$ 32
Bank premises and equipment held for sale	42	27	39
Branch Banking
Segment Reporting Information
Impairment of Branches and Land		7	32
Commercial Banking | Operating lease equipment
Segment Reporting Information
Other Asset Impairment Charges	45	$ 52	20	[1],[2]
General Corporate and Other
Segment Reporting Information
Bank premises and equipment held for sale	$ 42		$ 27

[1] These rates reflect the floating rates as of December 31, 2018 .

[2] Includes impairment charges of $ 20 for operating lease equipment.