Investment Securities, Part II (Details)	6 Months Ended
Jun. 30, 2017 USD ($) securities	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 99,695,000
After 1 through 5 years	402,914,000
After 5 through 10 years	174,999,000
After ten years	4,532,000
Fair Value	$ 682,140,000		$ 619,848,000
Available-for-sale, Weighted Average Yield, Maturities Year One (in hundredths)	2.14%
Available-for-sale , Weighted Average Yield, Maturities After 1 through 5 Years (in hundredths)	2.49%
Available-for-sale, Weighted Average Yield, Maturities After 5 through 10 Years (in hundredths)	2.62%
Available-for-sale , Weighted Average Yield, Maturities After 10 Years (in hundredths)	2.65%
Available-for-sale , Weighted Average Yield, Maturities (in hundredths)	2.47%
Available-for-sale, Full Tax-equivalent Yield, Maturities Year One (in hundredths)	2.54%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 1 through 5 Years (in hundredths)	2.89%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 5 through 10 years (in hundredths)	3.43%
Available-for-sale, Full Tax-equivalent Yield, Maturities After Ten Years (in hundredths)	3.60%
Available-for-sale, Full Tax-equivalent Yield, Maturities (in hundredths)	2.98%
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities	$ 74,281,000		74,231,000
Held To Maturity Weighted Average Yield Maturities Year One	1.79%
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	1.90%
Held To Maturity Tax Equivalent Yield Maturities Year One	1.79%
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	1.90%
Tax rate used to calculate tax-equivalent yields (in hundredths)	35.00%
Percentage investment book value exceeds total stockholders' equity (in hundredths)	10.00%
Investment Securities Pledged as Collateral	$ 495,000,000		509,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	209,478,000		484,981,000
Less than 12 months, Unrealized Losses	(2,299,000)		(9,411,000)
12 months or longer, Fair Value	9,547,000		9,525,000
12 months or longer, Unrealized losses	(769,000)		(1,673,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	219,025,000		494,506,000
Total Unrealized Losses	3,068,000		11,084,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 3,068,000		11,084,000
Details of Trust Preferred Securities [Abstract]
Coupon Rate of Trust Preferred Security	floating rate coupon of 3-month LIBOR plus 90 basis points
Number of Ratios Utilized in OTTI Credit Model	29
OTTI Cash Flow Initial Default Rate	2.00%
Period For Initial Default Rate Used In OTTI Analysis	two years
Default Rate Applied For Remainder Of OTTI Analysis	36 basis points
Recovery Rate Used In OTTI Cash Flow Analysis	10.00%
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)	0	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	1,111,000	$ 1,111,000
PreTSL XXVIII [Member]
Details of Trust Preferred Securities [Abstract]
Book Value	2,974,000
Fair Value	2,424,000
Unrealized Gains (Losses)	(550,000)
Other-than- temporary Impairment Recorded To-date	(1,111,000)
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	80,317,000
After 1 through 5 years	49,608,000
After 5 through 10 years	12,648,000
After ten years	0
Fair Value	142,573,000		136,324,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	44,993,000
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	29,288,000
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	0
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	0
Held-to-maturity Securities	74,281,000		74,231,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	81,271,000		125,257,000
Less than 12 months, Unrealized Losses	(1,068,000)		(2,508,000)
12 months or longer, Fair Value	0		0
12 months or longer, Unrealized losses	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	81,271,000		125,257,000
Total Unrealized Losses	1,068,000		2,508,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,068,000		2,508,000
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	44,558,000		53,295,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(462,000)		(1,338,000)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	44,558,000		53,295,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(462,000)		(1,338,000)
Obligations of states and political subdivisions
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	18,742,000
After 1 through 5 years	85,828,000
After 5 through 10 years	69,484,000
After ten years	1,958,000
Fair Value	176,012,000		162,705,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	32,928,000		93,405,000
Less than 12 months, Unrealized Losses	(434,000)		(2,804,000)
12 months or longer, Fair Value	0		0
12 months or longer, Unrealized losses	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	32,928,000		93,405,000
Total Unrealized Losses	434,000		2,804,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	434,000		2,804,000
Mortgage-backed securities: GSE residential
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	636,000
After 1 through 5 years	265,471,000
After 5 through 10 years	90,837,000
After ten years	0
Fair Value	356,944,000		314,991,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	95,279,000		266,319,000
Less than 12 months, Unrealized Losses	(797,000)		(4,099,000)
12 months or longer, Fair Value	7,123,000		5,878,000
12 months or longer, Unrealized losses	(219,000)		(270,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	102,402,000		272,197,000
Total Unrealized Losses	$ 1,016,000		$ 4,369,000
Number of securities in Unrealized Loss Positions \| securities	4		2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 1,016,000		$ 4,369,000
Trust preferred securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	0
After 1 through 5 years	0
After 5 through 10 years	0
After ten years	2,424,000
Fair Value	2,424,000		1,652,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	0		0
Less than 12 months, Unrealized Losses	0		0
12 months or longer, Fair Value	2,424,000		1,652,000
12 months or longer, Unrealized losses	(550,000)		(1,398,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,424,000		1,652,000
Total Unrealized Losses	$ 550,000		$ 1,398,000
Number of securities in Unrealized Loss Positions \| securities	1		1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 550,000		$ 1,398,000
Other securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	0
After 1 through 5 years	2,007,000
After 5 through 10 years	2,030,000
After ten years	150,000
Fair Value	4,187,000		4,176,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	0		0
Less than 12 months, Unrealized Losses	0		0
12 months or longer, Fair Value	0		1,995,000
12 months or longer, Unrealized losses	0		(5,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0		1,995,000
Total Unrealized Losses	0		$ 5,000
Number of securities in Unrealized Loss Positions \| securities			1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 0		$ 5,000

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.