Investment Securities (Details) $ in Thousands	3 Months Ended
Mar. 31, 2016 USD ($) securities	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Available-for-sale: [Abstract]
Amortized Cost	$ 512,310		$ 516,829
Gross Unrealized Gains	7,951		5,052
Gross Unrealized (Losses)	(1,922)		(3,033)
Fair Value	518,339		518,848
Gain (Loss) on Sale of Securities, Net	260	$ 229
Held-to-maturity: [Abstract]
Held-to-maturity Securities	97,382		85,208
Held-to-maturity Securities, Fair Value	98,362		85,737
Realized Investment Gains (Losses) [Abstract]
Gross gains	260	229
Gross losses	0	$ 0
U.S. Treasury securities and obligations of U.S. government corporations & agencies
Available-for-sale: [Abstract]
Amortized Cost	81,370		90,368
Gross Unrealized Gains	284		41
Gross Unrealized (Losses)	(106)		(268)
Fair Value	81,548		90,141
Held-to-maturity: [Abstract]
Held-to-maturity Securities	97,382		85,208
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	1,020		743
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(40)		(214)
Held-to-maturity Securities, Fair Value	98,362		85,737
Obligations of states and political subdivisions
Available-for-sale: [Abstract]
Amortized Cost	107,322		107,164
Gross Unrealized Gains	3,859		3,608
Gross Unrealized (Losses)	(53)		(55)
Fair Value	111,128		110,717
Mortgage-backed securities: GSE residential
Available-for-sale: [Abstract]
Amortized Cost	316,470		312,132
Gross Unrealized Gains	3,747		1,374
Gross Unrealized (Losses)	(325)		(1,452)
Fair Value	319,892		312,054
Trust preferred securities
Available-for-sale: [Abstract]
Amortized Cost	3,113		3,130
Gross Unrealized Gains	0		0
Gross Unrealized (Losses)	(1,415)		(1,224)
Fair Value	$ 1,698		1,906
Number of trust preferred securities \| securities	1
Trust preferred securities \| Maximum [Member]
Available-for-sale: [Abstract]
Maturities of Debt Securities	twenty-one years
Other securities
Available-for-sale: [Abstract]
Amortized Cost	$ 4,035		4,035
Gross Unrealized Gains	61		29
Gross Unrealized (Losses)	(23)		(34)
Fair Value	$ 4,073		$ 4,030

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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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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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