The yield on an available-for-sale government security, when the effect of reduced taxes are taken into account, for securities that mature. The full tax-equivalent yield show what yield a fully taxable security would have to give, in order to be equivalent to a tax free government security.

No definition available.

Investment Securities, Part II (Details)	3 Months Ended		6 Months Ended
Investment Securities, Part II (Details)	Jun. 30, 2018 USD ($) securities	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) securities	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 102,190,000		$ 102,190,000
After 1 through 5 years	221,842,000		221,842,000
After 5 through 10 years	256,623,000		256,623,000
After ten years	35,648,000		35,648,000
Fair Value	616,303,000		$ 616,303,000		$ 578,579,000
Available-for-sale, Weighted Average Yield, Maturities Year One (in hundredths)			2.35%
Available-for-sale , Weighted Average Yield, Maturities After 1 through 5 Years (in hundredths)			2.68%
Available-for-sale, Weighted Average Yield, Maturities After 5 through 10 Years (in hundredths)			2.92%
Available-for-sale , Weighted Average Yield, Maturities After 10 Years (in hundredths)			3.40%
Available-for-sale , Weighted Average Yield, Maturities (in hundredths)			2.77%
Available-for-sale, Full Tax-equivalent Yield, Maturities Year One (in hundredths)			2.52%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 1 through 5 Years (in hundredths)			3.05%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 5 through 10 years (in hundredths)			3.28%
Available-for-sale, Full Tax-equivalent Yield, Maturities After Ten Years (in hundredths)			3.43%
Available-for-sale, Full Tax-equivalent Yield, Maturities (in hundredths)			3.08%
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities	69,383,000		$ 69,383,000		69,332,000
Held To Maturity Weighted Average Yield Maturities Year One			1.76%
Held To Maturity Weighted Average Yield Maturities After 1 Through 5 Years			2.08%
Held To Maturity Weighted Average Yield Maturities After 5 Through 10 Years			0.00%
Held To Maturity Weighted Average Yield Maturities After 10 Years			0.00%
Held To Maturity Weighted Average Yield Maturities			2.68%
Held To Maturity Tax Equivalent Yield Maturities Year One			1.76%
Held To Maturity Tax Equivalent Yield Maturities After 1 Through 5 Years			2.08%
Held To Maturity Tax Equivalent Yield Maturities After 5 Through 10 Years			0.00%
Held To Maturity Tax Equivalent Yield Maturities After 10 Years			0.00%
Held To Maturity Tax Equivalent Yield Maturities			2.68%
Tax rate used to calculate tax-equivalent yields (in hundredths)			21.00%
Percentage investment book value exceeds total stockholders' equity (in hundredths)			10.00%
Investment Securities Pledged as Collateral	492,000,000		$ 492,000,000		479,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	358,734,000		358,734,000		289,151,000
Less than 12 months, Unrealized Losses	(7,954,000)		(7,954,000)		(3,251,000)
12 months or longer, Fair Value	131,319,000		131,319,000		82,396,000
12 months or longer, Unrealized losses	(6,476,000)		(6,476,000)		(2,613,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	490,053,000		490,053,000		371,547,000
Total Unrealized Losses	14,430,000		14,430,000		5,864,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	14,430,000		14,430,000		5,864,000
Credit losses on trust preferred securities held [Abstract]
Beginning of period			1,111,000	$ 1,111,000
Additions related to OTTI losses not previously recognized			0	0
Reductions due to sales / (recoveries)			(1,111,000)	0
Reductions due to change in intent or likelihood of sale			0	0
Additions related to increases in previously recognized OTTI losses			0	0
Reductions due to increases in expected cash flows			0	0
End of period	0	$ 1,111,000	0	1,111,000
Gain (Loss) on Sale of Securities, Net	881,000	$ 335,000	901,000	$ 335,000
U.S. Treasury securities and obligations of U.S. government corporations & agencies
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	85,405,000		85,405,000
After 1 through 5 years	37,633,000		37,633,000
After 5 through 10 years	0		0
After ten years	0		0
Fair Value	123,038,000		123,038,000		113,770,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	39,994,000		39,994,000
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	29,389,000		29,389,000
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	0		0
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	0		0
Held-to-maturity Securities	69,383,000		69,383,000		69,332,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	74,660,000		74,660,000		58,584,000
Less than 12 months, Unrealized Losses	(1,917,000)		(1,917,000)		(540,000)
12 months or longer, Fair Value	48,378,000		48,378,000		47,972,000
12 months or longer, Unrealized losses	(2,387,000)		(2,387,000)		(1,494,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	123,038,000		123,038,000		106,556,000
Total Unrealized Losses	$ 4,304,000		$ 4,304,000		$ 2,034,000
Number of securities in Unrealized Loss Positions \| securities	12		12		11
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 4,304,000		$ 4,304,000		$ 2,034,000
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	29,438,000		29,438,000		34,101,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(387,000)		(387,000)		(525,000)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	38,087,000		38,087,000		14,540,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,471,000)		(1,471,000)		(453,000)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	67,525,000		67,525,000		48,641,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (1,858,000)		$ (1,858,000)		$ (978,000)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions \| securities	7		7		7
Obligations of states and political subdivisions
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 16,785,000		$ 16,785,000
After 1 through 5 years	77,266,000		77,266,000
After 5 through 10 years	80,129,000		80,129,000
After ten years	1,060,000		1,060,000
Fair Value	175,240,000		175,240,000		$ 166,266,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	72,991,000		72,991,000		42,618,000
Less than 12 months, Unrealized Losses	(1,357,000)		(1,357,000)		(769,000)
12 months or longer, Fair Value	14,936,000		14,936,000		9,267,000
12 months or longer, Unrealized losses	(843,000)		(843,000)		(256,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	87,927,000		87,927,000		51,885,000
Total Unrealized Losses	$ 2,200,000		$ 2,200,000		$ 1,025,000
Number of securities in Unrealized Loss Positions \| securities	33		33		39
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 2,200,000		$ 2,200,000		$ 1,025,000
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	14,936,000		14,936,000		9,267,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(843,000)		(843,000)		(256,000)
Mortgage-backed securities: GSE residential
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	0		0
After 1 through 5 years	104,930,000		104,930,000
After 5 through 10 years	176,494,000		176,494,000
After ten years	34,247,000		34,247,000
Fair Value	315,671,000		315,671,000		293,811,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	211,083,000		211,083,000		187,949,000
Less than 12 months, Unrealized Losses	(4,680,000)		(4,680,000)		(1,942,000)
12 months or longer, Fair Value	68,005,000		68,005,000		22,609,000
12 months or longer, Unrealized losses	(3,246,000)		(3,246,000)		(518,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	279,088,000		279,088,000		210,558,000
Total Unrealized Losses	$ 7,926,000		$ 7,926,000		$ 2,460,000
Number of securities in Unrealized Loss Positions \| securities	28		28		26
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 7,926,000		$ 7,926,000		$ 2,460,000
Trust preferred securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	0		0
After 1 through 5 years	0		0
After 5 through 10 years	0		0
After ten years	0		0
Fair Value	0		0		2,548,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value					0
Less than 12 months, Unrealized Losses					0
12 months or longer, Fair Value					2,548,000
12 months or longer, Unrealized losses					(345,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value					2,548,000
Total Unrealized Losses					$ 345,000
Number of securities in Unrealized Loss Positions \| securities					1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0		0		$ 345,000
Credit losses on trust preferred securities held [Abstract]
Gain (Loss) on Sale of Securities, Net	846,000
Other securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	0		0
After 1 through 5 years	2,013,000		2,013,000
After 5 through 10 years	0		0
After ten years	341,000		341,000
Fair Value	2,354,000		2,354,000		2,184,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 0		$ 0		$ 0