Segments (Results of Operations and Average Assets by Segment) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information
Other Asset Impairment Charges			$ (9)	$ (36)
Unamortized debt issuance costs		$ 35		35	$ 34
Bank premises and equipment held for sale	$ 45		45		$ 81
Branch Banking
Segment Reporting Information
Impairment of Branches and Land	28	2	31	104
Commercial Banking | Operating lease equipment
Segment Reporting Information
Other Asset Impairment Charges	4	2	9	36
General Corporate and Other
Segment Reporting Information
Bank premises and equipment held for sale	$ 45	$ 81	$ 45	$ 81