Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)		6 Months Ended
	Jul. 01, 2020	Dec. 31, 2020	Jun. 30, 2020
Summary Of Significant Accounting Policies [Line Items]
Loans receivable allowance for credit loss		$ 63,386,000
Accrued interest receivable, writeoff		15,500,000
Available-for-sale securities accrued interest writeoff		4,100,000
Held-to-maturity securities accrued Interest writeoff		202,000
Accrued interest receivable		19,826,000	$ 17,373,000
Paycheck Protection Program (PPP) Loans [Member]
Summary Of Significant Accounting Policies [Line Items]
Accrued interest receivable		$ 0
ASU 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
Increase in allowance for credit loss	$ 20,200,000
Loans receivable allowance for credit loss	19,600,000
Unfunded commitments allowance for credit loss	536,000
Cumulative Effect Period Of Adoption Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of change in accounting principle for the adoption of ASU 2017-08			$ (14,239,000)
Cumulative Effect Period Of Adoption Adjustment [Member] | ASU 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of change in accounting principle for the adoption of ASU 2017-08	$ (14,200,000)