Loans and Lease Finance Receivables and Allowance for Loan Losses - Summary of Activity Related to Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Modifications [Line Items]
Total TDRs	$ 10,045	$ 30,051	$ 10,045	$ 30,051
Performing TDRs [Member]
Financing Receivable, Modifications [Line Items]
Beginning balance	16,574	20,292	19,233	42,687
New modifications	0	759	3,143	1,877
Payoffs and payments, net	(10,839)	(2,584)	(13,826)	(26,097)
TDRs returned to accrual status	0	8,551	329	8,551
TDRs placed on nonaccrual status	0	0	(3,144)	0
Ending balance	5,735	27,018	5,735	27,018
Nonperforming TDRs [Member]
Financing Receivable, Modifications [Line Items]
Beginning balance	4,391	12,029	1,626	12,622
New modifications	0	20	2,066	102
Charge-offs	0	0	0	(38)
Payoffs and payments, net	(81)	(465)	(2,197)	(1,102)
TDRs returned to accrual status	0	(8,551)	(329)	(8,551)
TDRs placed on nonaccrual status	0	0	3,144	0
Ending balance	$ 4,310	$ 3,033	$ 4,310	$ 3,033