Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013 Event	Dec. 31, 2012	Dec. 31, 2011
Goodwill [Line Items]
Acquisition of additional goodwill		$ 10,500,000
Acquisition of core deposits	3,200,000
Acquisition of wealth management relationships	100,000
Acquisition of insurance contract relationships	500,000
Number of triggering events	0
Amortization expense on finite-lived intangible assets	1,591,000	1,709,000	1,737,000
Mainline [Member]
Goodwill [Line Items]
Acquisition of additional goodwill		6,700,000
Gateway [Member]
Goodwill [Line Items]
Acquisition of additional goodwill		$ 3,800,000