Derivatives (Effects of Derivative Instruments on the Statements of Income) (Details) - Interest Rate Swaps Designated as Hedges [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	$ 6,952	$ (1,472)	$ 6,419
Other Noninterest Income [Member] | All Other Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	12,958	5,368	5,870
Fair Value Hedging [Member] | Interest Income [Member] | Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	1
Fair Value Hedging [Member] | Interest Expense [Member] | Brokered Deposits [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	(1,752)	(2,343)	829
Cash Flow Hedge [Member] | Interest Income [Member] | Variable Rate Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	$ (4,255)	$ (4,497)	$ (280)