Derivative Financial Instruments (Summary of Interest Rate Derivatives) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivative Assets
Gross Amounts Recognized	$ 103,644	$ 73,172
Derivative Liabilities
Gross Amounts Recognized	129,204	68,088
Interest rate derivatives
Derivative Assets
Gross Amounts Recognized	100,569	68,425
Less: Amounts offset in the Statements of Condition	0	0
Net amount presented in the Statements of Condition	100,569	68,425
Offsetting Derivative Positions	(2,561)	(28,124)
Collateral Posted	0	(23,810)
Net Credit Exposure	98,008	16,491
Derivative Liabilities
Gross Amounts Recognized	126,805	62,571
Less: Amounts offset in the Statements of Condition	0	0
Net amount presented in the Statements of Condition	126,805	62,571
Offsetting Derivative Positions	(2,561)	(28,124)
Collateral Posted	(124,244)	(2,640)
Net Credit Exposure	$ 0	$ 31,807