Premises and Equipment (Schedule of Premises and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total premises and equipment	$ 980,925	$ 953,815
Less: Accumulated depreciation and amortization	(546,618)	(527,002)
Premises and equipment, net	434,307	426,813
Land
Property, Plant and Equipment [Line Items]
Total premises and equipment	96,310	96,759
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment	392,952	388,254
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment	39,832	38,970
Furniture and equipment
Property, Plant and Equipment [Line Items]
Total premises and equipment	435,223	413,876
Construction in progress
Property, Plant and Equipment [Line Items]
Total premises and equipment	$ 16,608	$ 15,956