Goodwill and Other Intangible Assets - Summary of Core Deposit Intangibles (Detail) (Core deposit intangibles [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Core deposit intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Core deposit intangibles, Beginning balance	$ 8,074
Core deposit intangibles, Reductions/Amortization	0
Core deposit intangibles, Additions	0
Core deposit intangibles, Ending balance	8,074
Accumulated amortization, Beginning balance	(1,312)
Accumulated amortization, Reductions/Amortization	(289)
Accumulated amortization, Additions	0
Accumulated amortization, Ending balance	(1,023)
Core deposit intangibles, net, Beginning balance	6,762
Core deposit intangibles, net, Reductions/Amortization	(289)
Core deposit intangibles, net, Additions	0
Core deposit intangibles, net, Ending balance	$ 7,051