Bank Premises and Equipment - Summary of Bank Premises and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Cost	$ 71,785	$ 69,375
Accumulated Depreciation & Amortization	(37,280)	(34,910)
Net Carrying Value	34,505	34,465
Premises [Member]
Property, Plant and Equipment [Line Items]
Cost	49,647	48,064
Accumulated Depreciation & Amortization	(20,518)	(19,051)
Net Carrying Value	29,129	29,013
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	22,138	21,311
Accumulated Depreciation & Amortization	(16,762)	(15,859)
Net Carrying Value	$ 5,376	$ 5,452