Acquisitions and Divestitures (Narrative) (Details) $ in Thousands			1 Months Ended	3 Months Ended	9 Months Ended
	May 04, 2017 USD ($) branch	Apr. 03, 2017 USD ($)	Oct. 31, 2017 professional	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 16, 2016 USD ($)
Business Acquisition [Line Items]
Total assets				$ 29,622,636	$ 29,622,636		$ 28,555,231
Capital Bank Financial Corp
Business Acquisition [Line Items]
Total assets						$ 10,000,000
Number of bank branches operated | branch	193
Expected cash payment to acquire business, gross	$ 411,000
Percentage of outstanding common shares (percent)	29.00%
Total transaction value	$ 2,200,000
GE Capital
Business Acquisition [Line Items]
Loans acquired								$ 537,400
Coastal Securities
Business Acquisition [Line Items]
Payments to acquire business		$ 131,473
Goodwill		$ 45,000
FHN and Coastal
Business Acquisition [Line Items]
Acquisition-related expenses				$ 8,200	$ 14,600
Subsequent Event | Professional Mortgage Company, Inc. (PMC) [Member]
Business Acquisition [Line Items]
Number of professionals that joined CRE team | professional			11