Derivatives and Hedging Activities (Derivative Positions for Interest Rate Swaps which Qualify as Hedges) (Details) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Amortization Of Deferred Hedge Gains Losses		$ 0		$ 0
Change in Fair Value on Loans Held for Sale		413,000	$ 272,000	1,252,000	$ 1,192,000
Fair Value Hedges, Net		0		0		$ 0
Interest rate collars on loans [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Derivative, Notional Amount		$ 400,000,000		$ 400,000,000		$ 400,000,000
Derivative, Average Remaining Maturity				2 years 10 months 28 days		3 years 7 months 28 days
Derivative, Average Variable Interest Rate		0.15%		0.15%		1.76%
Fair Value	[1]	$ 24,169,000		$ 24,169,000		$ 9,896,000
Derivative, Average Cap Interest Rate		2.73%		2.73%		2.73%
Derivative, Average Floor Interest Rate		2.20%		2.20%		2.02%
Interest rate swaps on loans [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Derivative, Notional Amount		$ 450,000,000		$ 450,000,000		$ 450,000,000
Derivative, Average Remaining Maturity				2 years 10 months 28 days		3 years 7 months 28 days
Derivative, Average Variable Interest Rate		0.15%		0.15%		1.76%
Derivative, Average Fixed Interest Rate		2.37%		2.37%		2.37%
Fair Value	[1]	$ 29,878,000		$ 29,878,000		$ 12,907,000
Interest rate swaps on borrowings [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Derivative, Notional Amount		$ 75,000,000		$ 75,000,000		$ 75,000,000
Derivative, Average Remaining Maturity				1 year 5 months 4 days		2 years 2 months 4 days
Derivative, Average Variable Interest Rate		0.26%		0.26%		1.90%
Derivative, Average Fixed Interest Rate		1.53%		1.53%		1.53%
Fair Value	[1]	$ (1,561,000)		$ (1,561,000)		$ 140,000
Interest rate swaps
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Derivative, Notional Amount		925,000,000		925,000,000		925,000,000
Fair Value	[1]	$ 52,486,000		$ 52,486,000		$ 22,943,000

[1] Beginning in 2020, the Company made an election to include accrued interest within fair value balances.