Goodwill and Other Intangible Assets - Schedule of Definite-Lived Intangible Assets at Carrying Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets
Gross carrying amount	$ 75,410	$ 75,654
Accumulated amortization	(49,048)	(45,134)
Net carrying amount	26,362	30,520
Core Deposit Intangibles
Acquired Finite-Lived Intangible Assets
Gross carrying amount	74,001	74,001
Accumulated amortization	(48,074)	(43,957)
Net carrying amount	25,927	30,044
Customer Relationships Intangible Asset
Acquired Finite-Lived Intangible Assets
Gross carrying amount	1,348	1,348
Accumulated amortization	(962)	(984)
Net carrying amount	386	364
Non-Compete Agreements
Acquired Finite-Lived Intangible Assets
Gross carrying amount	61	100
Accumulated amortization	(12)	(79)
Net carrying amount	49	21
Other Intangible Assets
Acquired Finite-Lived Intangible Assets
Gross carrying amount	0	205
Accumulated amortization	0	(114)
Net carrying amount	$ 0	$ 91