Revenue from Contracts with Customers (Schedule of Disaggregation of Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Non-interest income		$ 129,572	$ 132,743	$ 370,750	$ 381,242
Revenue from Contracts with Customers In Scope of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		113,326	121,973	334,374	351,700
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Bank Card Transaction Fees [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		37,873	44,510	111,818	126,800
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Trust Fees [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		40,769	39,592	118,676	115,223
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Deposit Account Charges and Other Fees [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		23,107	24,032	69,063	71,009
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Consumer Brokerage Services [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		4,011	4,030	11,099	11,665
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Other Non-Interest Income [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		7,566	9,809	23,718	27,003
Revenue Not In Scope of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Non-interest income	[1]	$ 16,246	$ 10,770	$ 36,376	$ 29,542

[1] This revenue is not within the scope of ASU 2014-09, and includes fees relating to capital market activities, loan fees and sales, derivative instruments, standby letters of credit and various other transactions.