Goodwill and Other Intangible Assets - Schedule of Definite-Lived Intangible Assets at Carrying Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets
Gross carrying amount	$ 75,461	$ 75,654
Accumulated amortization	(47,067)	(45,134)
Net carrying amount	28,394	30,520
Core Deposit Intangibles
Acquired Finite-Lived Intangible Assets
Gross carrying amount	74,001	74,001
Accumulated amortization	(46,017)	(43,957)
Net carrying amount	27,984	30,044
Customer Relationships Intangible Asset
Acquired Finite-Lived Intangible Assets
Gross carrying amount	1,348	1,348
Accumulated amortization	(946)	(984)
Net carrying amount	402	364
Non-Compete Agreements
Acquired Finite-Lived Intangible Assets
Gross carrying amount	112	100
Accumulated amortization	(104)	(79)
Net carrying amount	8	21
Other Intangible Assets
Acquired Finite-Lived Intangible Assets
Gross carrying amount	0	205
Accumulated amortization	0	(114)
Net carrying amount	$ 0	$ 91