Loans Receivable and Allowance for Credit Losses (Narrative) (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) loan	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) loan	Dec. 31, 2022 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing Receivable, Accrued Interest, before Allowance for Credit Loss	$ 51,000		$ 50,900
Non-accrual	$ 47,592		$ 49,639
Number of loans 90 days past due and still accruing | loan	0		0
Provision charge (benefit) to operations	$ 200	$ 6,000
Impaired loan defined floor limit (greater than)	$ 1,000
Impaired loans number | loan	14		17
Impaired loans	$ 40,100		$ 42,300
Effect of adoption to allowance for credit loss	106,429	92,758	107,200	$ 88,023
Effect of adopting accounting standards updates	1,695,162	1,640,080	1,690,596	1,597,703
Total loans	10,842,707		10,873,701
Less than 90 days Past Due
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-accrual	4,600		23,200
RETAINED EARNINGS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of adopting accounting standards updates	988,480	940,533	974,542	918,158
Cumulative Effect, Period of Adoption, Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of adoption to allowance for credit loss				(594)
Effect of adopting accounting standards updates		433
Cumulative Effect, Period of Adoption, Adjustment | RETAINED EARNINGS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of adopting accounting standards updates		433		433
Purchased credit-impaired (PCI) loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of adoption to allowance for credit loss	1,600		1,700
Total loans	160,600		165,100
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	20,900		24,100
Commercial loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-accrual	36,892		41,487
Provision charge (benefit) to operations	7,924	(308)
Net chargeoff	971
Effect of adoption to allowance for credit loss	$ 38,292	$ 27,117	$ 31,475	27,413
Commercial loans | Cumulative Effect, Period of Adoption, Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of adoption to allowance for credit loss				$ (43)