Fair Value of Financial Instruments (Fair Values of Financial Assets and Liabilities on Balance Sheets) (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Cash and cash equivalents	$ 70,043,000	$ 66,146,000
Investment securities	878,200,000	859,538,000
Loans (1)	2,252,054,000	2,152,544,000
Bank premises and equipment, net	51,777,000	53,616,000
Bank owned life insurance	61,696,000	60,225,000
Financial liabilities:
Deposits	2,664,513,000	2,512,647,000
Short-term borrowings	193,717,000	305,607,000
Long-term borrowings	195,857,000	145,106,000
Cash flow hedges (2)	916,000	1,779,000
Carrying Amount
Financial assets:
Cash and cash equivalents	70,043,000	66,146,000
Investment securities	877,555,000	859,455,000
Loans (1)	2,311,696,000	2,210,529,000
Financial liabilities:
Deposits	2,664,682,000	2,509,722,000
Short-term borrowings	193,717,000	305,607,000
Long-term borrowings	195,890,000	$ 145,155,000
Cash flow hedges (2)	$ 916