Derivatives and Hedging Activities (Derivative Positions for Interest Rate Swaps which Qualify as Hedges) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Change in Fair Value on Loans Held for Sale	$ 305	$ 583	$ (1,459)	$ 839
Fair Value Hedges, Net	0		0		$ 0
Interest Receivable	29,900	$ 32,900	29,900	$ 32,900
Derivative, Net Liability Position, Aggregate Fair Value	42,200		42,200		79,800
Exposure to Institutional Counterparties	40,500		40,500		48,800
Exposure To Counterparties Relating To Customer Related Positions	81,700		81,700		127,200
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		$ 400,000		$ 400,000
Derivative, Average Remaining Maturity			2 years 2 months 1 day		2 years 7 months 28 days
Derivative, Average Variable Interest Rate	0.08%		0.08%		0.15%
Fair Value	$ 15,964		$ 15,964		$ 21,764
Derivative, Average Cap Interest Rate	2.73%		2.73%		2.73%
Derivative, Average Floor Interest Rate	2.20%		2.20%		2.20%
Interest rate swaps on loans [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Derivative, Notional Amount	$ 550,000		$ 550,000		$ 450,000
Derivative, Average Remaining Maturity			3 years 29 days		2 years 7 months 28 days
Derivative, Average Variable Interest Rate	0.09%		0.09%		0.15%
Derivative, Average Fixed Interest Rate	2.16%		2.16%		2.37%
Fair Value	$ 20,985		$ 20,985		$ 27,021
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		$ 75,000		$ 75,000
Derivative, Average Remaining Maturity			8 months 4 days		1 year 2 months 4 days
Derivative, Average Variable Interest Rate	0.13%		0.13%		0.22%
Derivative, Average Fixed Interest Rate	1.53%		1.53%		1.53%
Fair Value	$ (845)		$ (845)		$ (1,341)
Interest rate swaps
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Derivative, Notional Amount	1,025,000		1,025,000		925,000
Fair Value	36,104		36,104		47,444
Interest Receivable	1,200		1,200		1,200
Interest Payable, Current	$ (58)		$ (58)		$ (81)