Loans and Lease Finance Receivables and Allowance for Loan Losses - Schedule of Recorded Investment in Loans Held-for-Investment and Related Allowance for Loan Losses by Loan Type (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	$ 37,764		$ 67,390
Recorded Investment in Loans, Collectively Evaluated for Impairment	4,134,444		3,620,291
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	76,022		110,746
Allowance for Loan Losses, Individually Evaluated for Impairment	630		550
Allowance for Loan Losses, Collectively Evaluated for Impairment	59,998		59,004
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	310		0
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	1,447		1,562
Recorded Investment in Loans, Collectively Evaluated for Impairment	477,686		404,861
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	526		435
Allowance for Loan Losses, Collectively Evaluated for Impairment	8,861		6,750
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
Small Business Administration [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	3,498		3,146
Recorded Investment in Loans, Collectively Evaluated for Impairment	108,264		117,420
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	42		12
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,135		2,073
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	17,908		39,981
Recorded Investment in Loans, Collectively Evaluated for Impairment	2,866,424		2,529,430
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	1		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	39,918		35,414
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	7,651		7,651
Recorded Investment in Loans, Collectively Evaluated for Impairment	86,358		39,276
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	45		24
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,183		722
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
SFR Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	5,734		7,044
Recorded Investment in Loans, Collectively Evaluated for Impairment	231,754		207,459
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	13		77
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,488		2,487
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	697		7,091
Recorded Investment in Loans, Collectively Evaluated for Impairment	213,133		176,893
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	4,882		3,974
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
Municipal Lease Finance Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	71,929		74,691
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,115		1,014
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
Consumer and Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	829		915
Recorded Investment in Loans, Collectively Evaluated for Impairment	78,896		70,261
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	3		2
Allowance for Loan Losses, Collectively Evaluated for Impairment	416		832
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	0		0
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	0		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	0		5,738
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	0		0
PCI Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	0		0
Recorded Investment in Loans, Acquired with Deteriorated Credit Quality	76,022	$ 93,712	110,746
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	0		0
Allowance for Loan Losses, Acquired with Deteriorated Credit Quality	$ 310		$ 0