Segments (Results of Operations and Average Assets by Segment) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016		Dec. 31, 2016
Segment Reporting Information
Other Asset Impairment Charges	$ (20)	$ 0	[1]
Bank premises and equipment held for sale	51			$ 39
Net tax deficiency reclassified from capital surplus to applicable income tax expense		1
Branch Banking
Segment Reporting Information
Impairment of Branches and Land	3	2
Bank premises and equipment held for sale	51	68
Commercial Banking | Operating lease equipment
Segment Reporting Information
Other Asset Impairment Charges	$ 31
General Corporate and Other
Segment Reporting Information
Net tax deficiency reclassified from capital surplus to applicable income tax expense		$ 1

[1] A net tax deficiency of $ 1 million was reclassified from capital surplus to applicable income tax expense at March 31, 2016, related to the early adoption of ASU 2016-09 during the fourth quarter of 2016, with an effective date of January 1, 2016.