Revenue from Contracts with Customers (Schedule of Disaggregation of Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Non-interest income		$ 121,240	$ 119,690
Revenue from Contracts with Customers In Scope of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		112,037	111,576
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Bank Card Transaction Fees [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		39,644	41,453
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Trust Fees [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		37,256	36,062
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		23,018	22,982
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Consumer Brokerage Services [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		3,747	3,768
Revenue from Contracts with Customers In Scope of ASC 606 [Member] | Other Non-Interest Income [Member]
Disaggregation of Revenue [Line Items]
Non-interest income		8,372	7,311
Revenue Not In Scope of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Non-interest income	[1]	$ 9,203	$ 8,114

[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.