Variable Interest Entities (VIEs) (Impact Of VIEs On The Consolidated Statements Of Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Other noninterest income									$ 111	$ 102	$ 102
Provision for income taxes	$ 218	$ 108	$ 99	$ 66	$ 62	$ 64	$ 42	$ 25	491	193	229
Variable Interest Entity
Variable Interest Entity [Line Items]
Other noninterest income									2	(1)	1
Provision for income taxes, amortization of LIHTC investments									67	66	62
Provision for income taxes									(20)	(22)	(21)
Low income housing tax credits | Variable Interest Entity
Variable Interest Entity [Line Items]
Provision for income taxes, affordable housing tax credits and other tax benefits									(63)	(62)	(61)
Other tax benefits related to tax credit entities | Variable Interest Entity
Variable Interest Entity [Line Items]
Provision for income taxes, affordable housing tax credits and other tax benefits									$ (24)	$ (26)	$ (22)