Derivatives and Hedging Activities (Derivative Positions for Interest Rate Swaps which Qualify as Hedges) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021	Mar. 31, 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	$ (1,764)	$ 255
Fair Value Hedges, Net	0		$ 0
Interest Receivable	33,400	$ 25,900
Derivative, Net Liability Position, Aggregate Fair Value	28,500		79,800
Exposure to Institutional Counterparties	50,900		48,800
Exposure To Counterparties Relating To Customer Related Positions	76,800		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
Derivative, Average Remaining Maturity	2 years 4 months 28 days		2 years 7 months 28 days
Derivative, Average Variable Interest Rate	0.11%		0.15%
Fair Value	$ 17,942		$ 21,764
Derivative, Average Cap Interest Rate	2.73%		2.73%
Derivative, Average Floor Interest Rate	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		$ 450,000
Derivative, Average Remaining Maturity	3 years 3 months 29 days		2 years 7 months 28 days
Derivative, Average Variable Interest Rate	0.10%		0.15%
Derivative, Average Fixed Interest Rate	2.16%		2.37%
Fair Value	$ 21,467		$ 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
Derivative, Average Remaining Maturity	11 months 4 days		1 year 2 months 4 days
Derivative, Average Variable Interest Rate	0.19%		0.22%
Derivative, Average Fixed Interest Rate	1.53%		1.53%
Fair Value	$ (1,075)		$ (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		925,000
Fair Value	38,334		47,444
Interest Receivable	1,200		1,200
Interest Payable, Current	$ (56)		$ (81)

Change in Fair Value on Loans Held for Sale

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- Definition

Exposure to counterparties relating to customer related positions.

+ References

No definition available.

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Exposure to Institutional Counterparties relating to the company's derivative portfolio.

+ References

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- Definition

Average cap rate on a group of interest rate derivatives, such as interest rate caps or collars. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

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Average fixed interest rate related to the group of interest rate derivatives.

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- Definition

Average floor rate on a group of interest rate derivatives, such as interest rate floor or collars. If market rates fall below the floor rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

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Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Average variable interest rate related to the group of interest rate derivatives.

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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- Definition

Nominal or face amount used to calculate payment on derivative.

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- Definition

Net fair value of all derivative instruments designated as fair value hedging instruments.

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- Definition

Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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