Schedule of Remaining Contractual Maturities of Repurchase Agreements by Type of Collateral Pledged (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 134,661	$ 138,614
Municipal securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	1,447
U.S. Agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	69,754
Mortgage-backed Agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	63,460
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	82,248
Overnight and Continuous | U.S. Agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	69,754
Overnight and Continuous | Mortgage-backed Agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	12,494
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	174
Up to 30 Days | Mortgage-backed Agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	174
30-90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	285
30-90 Days | Mortgage-backed Agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	285
Greater Than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	51,954
Greater Than 90 Days | Municipal securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	1,447
Greater Than 90 Days | Mortgage-backed Agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 50,507