Securities (Schedule of Securities Available-for-Sale) (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 997,074,000	$ 834,850,000
Gross Unrealized Gains	40,885,000	21,780,000
Gross Unrealized Losses	(1,049,000)	(1,805,000)
Allowance for Credit Losses	0
Fair Value	1,036,910,000	854,825,000
Obligations of State and Political Subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	489,070,000	307,943,000
Gross Unrealized Gains	25,928,000	16,366,000
Gross Unrealized Losses	(986,000)	(9,000)
Allowance for Credit Losses	0
Fair Value	514,012,000	324,300,000
MBS/CMO
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	508,004,000	526,907,000
Gross Unrealized Gains	14,957,000	5,414,000
Gross Unrealized Losses	(63,000)	(1,796,000)
Allowance for Credit Losses	0
Fair Value	$ 522,898,000	$ 530,525,000