Loans and Leases Receivable and Allowance for Loan and Lease Losses - Loans by Type and Performance Status (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	$ 35,123	$ 15,551
Non-Accrual	20,021	27,494
Current	7,244,271	7,073,879
Total loans	$ 7,316,903	7,138,498
Due days for loan payments (days)	30 days
Delinquent period (days)	90 days
30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	$ 33,329	13,363
90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	1,794	2,188
Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	17,488	21,574
Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,133	0
Non-Accrual	4,117	1,155
Current	1,901,336	3,282,452
Total loans	1,909,274	3,285,297
Multi-family | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,133	0
Multi-family | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Multi-family | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,688	1,690
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,395	1,914
Non-Accrual	4,531	17,764
Current	1,882,700	1,353,586
Total loans	1,889,980	1,373,800
Commercial and industrial | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,395	1,914
Commercial and industrial | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Commercial and industrial | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	354	536
Commercial real estate owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	5,388	193
Non-Accrual	1,963	1,037
Current	537,992	567,809
Total loans	552,007	577,477
Commercial real estate owner occupied | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	5,388	193
Commercial real estate owner occupied | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Commercial real estate owner occupied | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,664	8,438
Commercial real estate non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	8,034	1,190
Non-Accrual	76	129
Current	1,211,892	1,119,443
Total loans	1,223,529	1,125,106
Commercial real estate non-owner occupied | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	8,034	1,190
Commercial real estate non-owner occupied | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Commercial real estate non-owner occupied | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,527	4,344
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Non-Accrual	0	0
Current	118,418	56,491
Total loans	118,418	56,491
Construction | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Construction | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Construction | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	5,924	5,940
Non-Accrual	6,128	5,605
Current	359,491	550,679
Total loans	375,014	566,561
Residential real estate | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	5,924	5,940
Residential real estate | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Residential real estate | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,471	4,337
Manufactured housing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	5,493	6,114
Non-Accrual	1,655	1,693
Current	61,649	69,916
Total loans	70,398	79,731
Cash	100	500
Manufactured housing | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	3,699	3,926
Manufactured housing | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	1,794	2,188
Manufactured housing | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,601	2,008
Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	5,756	200
Non-Accrual	1,551	111
Current	1,170,793	73,503
Total loans	1,178,283	74,035
Other consumer | 30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	5,756	200
Other consumer | 90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Other consumer | Purchased credit impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 183	$ 221