Premises And Equipment - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Premises and Equipment Additional Information [Line Items]
Depreciation and amortization	$ 7,847,000	$ 7,488,000	$ 7,686,000
Operating Leases, Rent Expense, Net	6,600,000	5,900,000	5,900,000
Maximum
Premises and Equipment Additional Information [Line Items]
Lease Commitment Initial Term	15 years
Maximum | Ground Lease
Premises and Equipment Additional Information [Line Items]
Lease Commitment Initial Term	20 years
Minimum
Premises and Equipment Additional Information [Line Items]
Lease Commitment Initial Term	3 years
Premises and Equipment
Premises and Equipment Additional Information [Line Items]
Depreciation and amortization	$ 4,500,000	$ 4,300,000	$ 4,300,000