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, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	$ 14,506	$ 14,712
Recorded Investment in Loans, Collectively Evaluated for Impairment	7,525,662	4,788,193
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		19,426
Allowance for Loan Losses, Individually Evaluated for Impairment	371	16
Allowance for Loan Losses, Collectively Evaluated for Impairment	66,761	59,351
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		216
PCI Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment		0
Recorded Investment in Loans, Collectively Evaluated for Impairment		0
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		19,426
Allowance for Loan Losses, Individually Evaluated for Impairment		0
Allowance for Loan Losses, Collectively Evaluated for Impairment		0
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		216
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	2,088	355
Recorded Investment in Loans, Collectively Evaluated for Impairment	915,865	508,833
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	276	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	7,581	6,970
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		0
Small Business Administration [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	5,632	1,174
Recorded Investment in Loans, Collectively Evaluated for Impairment	321,974	119,874
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	93	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,026	841
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		0
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	1,531	7,741
Recorded Investment in Loans, Collectively Evaluated for Impairment	5,415,820	3,446,289
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	48,287	42,597
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		0
Construction [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	116,457	84,400
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	871	1,003
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		0
SFR Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	4,858	4,133
Recorded Investment in Loans, Collectively Evaluated for Impairment	273,427	233,021
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0	13
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,323	2,142
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		0
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	0	800
Recorded Investment in Loans, Collectively Evaluated for Impairment	301,752	267,689
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	5,341	4,351
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		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	59,985	67,721
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	726	808
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		0
Consumer and Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment in Loans, Individually Evaluated for Impairment	397	509
Recorded Investment in Loans, Collectively Evaluated for Impairment	120,382	60,366
Recorded Investment in Loans, Acquired with Deterioriated Credit Quality		0
Allowance for Loan Losses, Individually Evaluated for Impairment	2	3
Allowance for Loan Losses, Collectively Evaluated for Impairment	$ 606	639
Allowance for Loan Losses, Acquired with Deterioriated Credit Quality		$ 0