Goodwill and Other Intangible Assets - Summary of Changes in Carrying Amount of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 57,517	$ 56,238
Goodwill, Acquired During Period	10,200	1,279
Goodwill, Ending Balance	67,717	57,517
Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	35,058	35,058
Goodwill, Acquired During Period	0	0
Goodwill, Ending Balance	35,058	35,058
Wealth Management [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	8,625	8,625
Goodwill, Acquired During Period	6,809	0
Goodwill, Ending Balance	15,434	8,625
Insurance [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	13,834	12,555
Goodwill, Acquired During Period	3,391	1,279
Goodwill, Ending Balance	$ 17,225	$ 13,834