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Investment Securities (Narrative) (Details)
 12 Months Ended
Dec. 31, 2021
USD ($)
Segment
Security
Dec. 31, 2020
USD ($)
Security
Dec. 31, 2019
USD ($)
Schedule Of Investments [Line Items]      
Securities pledged as collateral $ 637,600,000 $ 567,400,000  
Number of security positions, unrealized loss position 116 8  
Number of security positions, unrealized loss position for more than 12 months | Security 28 1  
Securities, 12 months or longer, Fair Value $ 172,180,000 $ 8,000  
Securities, 12 months or longer, Unrealized Losses $ 4,727,000    
Number of security positions, unrealized loss position for less than 12 months | Security 88 70  
Securities, Less than 12 months, Fair Value $ 773,484,000 $ 29,087,000  
Securities, Less than 12 months, Unrealized Losses 10,039,000 68,000  
Available for sale securities, allowance for credit loss 0    
Debt securities, held-to-maturity 205,586,000 271,973,000  
Investment securities, past due 3,631,355,000 3,557,908,000 $ 3,179,465,000
Investment securities, nonaccrual 11,369,000 9,286,000  
Municipal Bonds [Member]      
Schedule Of Investments [Line Items]      
Debt securities, held-to-maturity 105,600,000 135,700,000  
Internally rated held-to-maturity securities 5,800,000 8,500,000  
Municipal Bonds [Member] | Below Investment Grade [Member]      
Schedule Of Investments [Line Items]      
Investment grade rating exposure   $ 279,000  
Investment grade rating exposure percentage   0.19%  
Maximum [Member]      
Schedule Of Investments [Line Items]      
Securities, 12 months or longer, Unrealized Losses   $ 1,000  
Total Past Due [Member]      
Schedule Of Investments [Line Items]      
Investment securities, past due 9,467,000 7,994,000  
Available for Sale Securities [Member]      
Schedule Of Investments [Line Items]      
Accrued interest receivable 2,100,000 1,200,000  
Held-to-maturity Securities [Member]      
Schedule Of Investments [Line Items]      
Accrued interest receivable 696,000 905,000  
Investment securities, nonaccrual 0    
Held-to-maturity Securities [Member] | Maximum [Member]      
Schedule Of Investments [Line Items]      
Credit Loss Benefit Expense (5,000) $ (7,000)  
Held-to-maturity Securities [Member] | Total Past Due [Member]      
Schedule Of Investments [Line Items]      
Investment securities, past due $ 0