Investment Securities (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) securities	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Available-for-sale: [Abstract]
Amortized Cost	$ 677,461		$ 677,461		$ 628,895
Gross Unrealized Gains	7,747		7,747		2,037
Gross Unrealized (Losses)	(3,068)		(3,068)		(11,084)
Fair Value	682,140		682,140		619,848
Gain (Loss) on Sale of Securities, Net	335	$ 404	335	$ 664
Held-to-maturity: [Abstract]
Held-to-maturity Securities	74,281		74,281		74,231
Held-to-maturity Securities, Fair Value	74,224		74,224		73,096
Realized Investment Gains (Losses) [Abstract]
Gross gains	352	404	352	664
Gross losses	(17)	$ 0	(17)	$ 0
U.S. Treasury securities and obligations of U.S. government corporations & agencies
Available-for-sale: [Abstract]
Amortized Cost	143,014		143,014		138,819
Gross Unrealized Gains	627		627		13
Gross Unrealized (Losses)	(1,068)		(1,068)		(2,508)
Fair Value	142,573		142,573		136,324
Held-to-maturity: [Abstract]
Held-to-maturity Securities	74,281		74,281		74,231
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	405		405		203
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(462)		(462)		(1,338)
Held-to-maturity Securities, Fair Value	74,224		74,224		73,096
Obligations of states and political subdivisions
Available-for-sale: [Abstract]
Amortized Cost	172,446		172,446		164,163
Gross Unrealized Gains	4,000		4,000		1,346
Gross Unrealized (Losses)	(434)		(434)		(2,804)
Fair Value	176,012		176,012		162,705
Mortgage-backed securities: GSE residential
Available-for-sale: [Abstract]
Amortized Cost	354,993		354,993		318,829
Gross Unrealized Gains	2,967		2,967		531
Gross Unrealized (Losses)	(1,016)		(1,016)		(4,369)
Fair Value	356,944		356,944		314,991
Trust preferred securities
Available-for-sale: [Abstract]
Amortized Cost	2,974		2,974		3,050
Gross Unrealized Gains	0		0		0
Gross Unrealized (Losses)	(550)		(550)		(1,398)
Fair Value	2,424		$ 2,424		1,652
Number of trust preferred securities \| securities			1
Trust preferred securities \| Maximum [Member]
Available-for-sale: [Abstract]
Maturities of Debt Securities			twenty years
Other securities
Available-for-sale: [Abstract]
Amortized Cost	4,034		$ 4,034		4,034
Gross Unrealized Gains	153		153		147
Gross Unrealized (Losses)	0		0		(5)
Fair Value	$ 4,187		$ 4,187		$ 4,176

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Amount of investments in debt securities classified as available-for-sale, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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