Loans, Leases and Allowance for Credit Losses - Changes in Accretable Discount for Loans Purchased with Credit Quality Deterioration (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		$ 15,925	$ 19,156
Reclassifications from non-accretable to accretable yield (1)	[1]	0	430
Accretion to interest income		(782)	(1,078)
Reversal of fair value adjustments upon disposition of loans		(1,602)	(552)
Balance at end of period		$ 13,541	$ 17,956

[1] The primary drivers of reclassification from non-accretable to accretable yield resulted from changes in estimated cash flows.