Segments (Results of Operations and Average Assets by Segment) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016		Dec. 31, 2016
Segment Reporting Information
Other Asset Impairment Charges			$ (19)	$ (5)	[1]
Bank premises and equipment held for sale	$ 41		41			$ 39
Net tax deficiency reclassified from capital surplus to applicable income tax expense		$ 5		6
Branch Banking
Segment Reporting Information
Impairment of Branches and Land	2	1	5	3
Commercial Banking | Operating lease equipment
Segment Reporting Information
Other Asset Impairment Charges		5	31	5
General Corporate and Other
Segment Reporting Information
Bank premises and equipment held for sale	$ 41	52	$ 41	52
Net tax deficiency reclassified from capital surplus to applicable income tax expense		$ 5		$ 6

[1] Net tax deficiencies of $ 6 were reclassified from capital surplus to applicable income tax expense for the six months ended June 30, 2016, related to the early adoption of ASU 2016-09 during the fourth quarter of 2016, with an effective date of January 1, 2016.