Loans Receivable and Allowance for Credit Losses (Narrative) (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022 USD ($) loan	Dec. 31, 2022 USD ($) loan	Mar. 31, 2023 USD ($) loan	Dec. 31, 2021 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount of nonaccrual loans		$ 58,500	$ 35,500
Loans less than 90 days past due		$ 42,900	$ 11,900
Number of loans 90 days past due and still accruing | loan		0	0
Impaired loan defined floor limit (greater than)			$ 1,000
Impaired loans number | loan	15	10
Impaired loans		$ 42,800	27,500
Allowance for credit losses	$ 76,275	88,023	92,758	$ 80,740
Cumulative effect adjustment increase	1,621,131	1,597,703	$ 1,640,080	1,697,096
Charge off, impaired loan	$ 0
Number of payment defaults for loans modified as TDRs | loan	0
Number of PPP loans | loan			2,067
Paycheck protection program			$ 682,000
Number of loans forgiven | loan			2,054
Paycheck protection program, amount forgiven			$ 679,300
Paycheck protection program, amount outstanding			2,700
Loans		10,248,883	10,224,214
RETAINED EARNINGS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative effect adjustment increase	$ 839,807	918,158	940,533	814,533
Cumulative Effect, Period of Adoption, Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowance for credit losses		(594)
Cumulative effect adjustment increase		433
Cumulative Effect, Period of Adoption, Adjustment | RETAINED EARNINGS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative effect adjustment increase		433
Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured for impairment based on the fair value of the underlying collateral		24,000	5,200
Purchased credit-impaired (PCI) loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowance for credit losses		1,700	1,600
Loans		193,000	176,800
Commercial Loan | Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured for impairment based on the fair value of the underlying collateral			5,200
Commercial Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowance for credit losses	$ 23,799	27,413	$ 27,117	$ 26,343
Commercial Loans | Cumulative Effect, Period of Adoption, Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowance for credit losses		$ (43)