Premises And Equipment (Additional Information) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Operating Leases, Rent Expense, Net	$ 7,600,000	$ 7,400,000	$ 6,600,000
Maximum
Property, Plant and Equipment [Line Items]
Lease Commitment Initial Term	15 years
Minimum
Property, Plant and Equipment [Line Items]
Lease Commitment Initial Term	3 years
Ground Lease | Maximum
Property, Plant and Equipment [Line Items]
Lease Commitment Initial Term	20 years
Premises and Equipment
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 4,600,000	$ 4,600,000	$ 4,500,000