Investment Securities (Narrative) (Details)	3 Months Ended
	Mar. 31, 2024 USD ($) Security	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) Security
Schedule Of Investments [Line Items]
Securities pledged as collateral	$ 1,020,000,000.00		$ 845,200,000
Proceeds from Sale of Debt Securities, Available-for-Sale	$ 0	$ 0
Number of security positions, unrealized loss position | Security	201		201
Number of security positions, unrealized loss position for more than 12 months | Security	197		198
Securities, 12 months or longer, Fair Value	$ 809,521,000		$ 835,522,000
Securities, 12 months or longer, Unrealized Losses	$ 160,845,000		$ 151,546,000
Number of security positions, unrealized loss position for less than 12 months | Security	4		3
Securities, Less than 12 months, Fair Value	$ 64,697,000		$ 8,000
Securities, Less than 12 months, Unrealized Losses	1,000		0
Available for sale securities, allowance for credit loss	0		0
Securities held to maturity, Amortized Cost	143,717,000		148,160,000
Internally rated held-to-maturity securities	$ 4,100,000		$ 4,200,000
Investment, Type [Extensible Enumeration]	Municipal Bonds [Member]		Municipal Bonds [Member]
Investment securities, past due	$ 4,397,864,000		$ 4,416,251,000
Total Past Due [Member]
Schedule Of Investments [Line Items]
Investment securities, past due	12,906,000		29,347,000
Municipal Bonds [Member]
Schedule Of Investments [Line Items]
Securities held to maturity, Amortized Cost	62,300,000		64,600,000
Maximum [Member]
Schedule Of Investments [Line Items]
Securities, 12 months or longer, Unrealized Losses	160,800,000		151,500,000
Securities, Less than 12 months, Unrealized Losses	1,000		1,000
Available for Sale Securities [Member]
Schedule Of Investments [Line Items]
Accrued interest receivable	2,000,000		2,100,000
Held To Maturity Investment Securities [Member]
Schedule Of Investments [Line Items]
Accrued interest receivable	783,000		571,000
Held To Maturity Investment Securities [Member] | Total Past Due [Member]
Schedule Of Investments [Line Items]
Investment securities, past due	0		$ 0
Held To Maturity Investment Securities [Member] | Maximum [Member]
Schedule Of Investments [Line Items]
Provision for credit loss	$ 1,000	$ 1,000