Acquisitions/Dispositions Acquisitions/Dispositions - Additional Information (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 15, 2016
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	[1]				$ 14
Noninterest Expense		$ 5,468	$ 5,160	$ 5,543
Revenues		3,383	3,268	3,323
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		2,830	2,849	2,420
Gain (Loss) on Disposition of Business		0	0	105
Proceeds from Divestiture of Businesses		0	0	193
Business Combination, Consideration Transferred		(197)
Loans Held For Investment [Member] | Pillar Financial [Member]
Principal Amount Outstanding of Loans Held-in-portfolio					38
Loans Held For Sale [Member] | Pillar Financial [Member]
Principal Amount Outstanding of Loans Held-in-portfolio					180
Commercial Mortgage Servicing Rights [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets					$ 62
Corporate Other [Member]
Noninterest Expense		5	4	134
Revenues		136	135	278
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		$ 229	$ 281	422
Corporate Other [Member] | Ridgeworth Capital Management [Member]
Noninterest Expense				59
Revenues				81
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest				22
Ridgeworth Capital Management [Member]
Net Assets				96
Stockholders' Equity Attributable to Noncontrolling Interest				23
Assets under Management, Carrying Amount				$ 49,100

[1] Does not include servicing rights acquired.