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Investment Securities, Part II (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) securities	Dec. 31, 2016 USD ($) securities	Dec. 31, 2015 USD ($) securities	Dec. 31, 2014 USD ($)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 82,570,000	$ 82,570,000
After 1 through 5 years	253,615,000	253,615,000
After 5 through 10 years	281,080,000	281,080,000
After ten years	2,583,000	2,583,000
Fair Value	619,848,000	$ 619,848,000	$ 518,848,000
Available-for-sale, Weighted Average Yield, Maturities Year One (in hundredths)		2.12%
Available-for-sale , Weighted Average Yield, Maturities After 1 through 5 Years (in hundredths)		2.36%
Available-for-sale, Weighted Average Yield, Maturities After 5 through 10 Years (in hundredths)		2.63%
Available-for-sale , Weighted Average Yield, Maturities After 10 Years (in hundredths)		2.20%
Available-for-sale , Weighted Average Yield, Maturities (in hundredths)		2.45%
Available-for-sale, Full Tax-equivalent Yield, Maturities Year One (in hundredths)		2.49%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 1 through 5 Years (in hundredths)		2.93%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 5 through 10 years (in hundredths)		3.07%
Available-for-sale, Full Tax-equivalent Yield, Maturities After Ten Years (in hundredths)		2.71%
Available-for-sale, Full Tax-equivalent Yield, Maturities (in hundredths)		2.93%
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	44,992,000	$ 44,992,000
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	29,239,000	29,239,000
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, at amortized cost (estimated fair value of $73,096 at December 31, 2016 and $85,737 at December 31, 2015)	74,231,000	$ 74,231,000	85,208,000
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	509,296,000	$ 509,296,000	404,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	484,981,000	484,981,000	204,325,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	9,411,000	9,411,000	1,049,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	9,525,000	9,525,000	35,867,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,673,000	1,673,000	1,984,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	494,506,000	494,506,000	240,192,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 11,084,000	11,084,000	3,033,000
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	$ 1,111,000
Additions related to OTTI losses not previously recognized		0	0	0
Reductions due to sales / (recoveries)		0	0	0
Reductions due to change in intent or likelihood of sale		0	0	0
Additions related to increases in previously recognized OTTI losses		0	0	0
Reductions due to increases in expected cash flows		0	0	0
End of period	$ 1,111,000	1,111,000	1,111,000	$ 1,111,000
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	43,798,000	43,798,000
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	29,298,000	29,298,000
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	0	0
Held-to-maturity Securities, Debt Maturities, after Ten Years, Fair Value	0	0
Held-to-maturity Securities, Fair Value	73,096,000	73,096,000	85,737,000
PreTSL XXVIII
Details of Trust Preferred Securities [Abstract]
Book Value	3,050,000	3,050,000
Market Value	1,652,000	1,652,000
Unrealized Gains (Losses)	(1,398,000)	(1,398,000)
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	67,138,000	67,138,000
After 1 through 5 years	42,647,000	42,647,000
After 5 through 10 years	26,539,000	26,539,000
After ten years	0	0
Fair Value	136,324,000	136,324,000	90,141,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	44,992,000	44,992,000
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	29,239,000	29,239,000
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, at amortized cost (estimated fair value of $73,096 at December 31, 2016 and $85,737 at December 31, 2015)	74,231,000	74,231,000	85,208,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	125,257,000	125,257,000	34,942,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,508,000	2,508,000	142,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	0	12,971,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	126,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	125,257,000	125,257,000	47,913,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	2,508,000	2,508,000	$ 268,000
Number of securities in Unrealized Loss Positions			6
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	53,295,000	53,295,000	$ 35,845,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,338,000)	(1,338,000)	(214,000)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	53,295,000	53,295,000	35,845,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,338,000)	(1,338,000)	(214,000)
Credit losses on trust preferred securities held [Abstract]
Held-to-maturity Securities, Fair Value	73,096,000	73,096,000	85,737,000
Obligations of states and political subdivisions
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	14,860,000	14,860,000
After 1 through 5 years	83,676,000	83,676,000
After 5 through 10 years	63,382,000	63,382,000
After ten years	787,000	787,000
Fair Value	162,705,000	162,705,000	110,717,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	93,405,000	93,405,000	3,168,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,804,000	2,804,000	32,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	0	979,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	23,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	93,405,000	93,405,000	4,147,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	2,804,000	2,804,000	$ 55,000
Number of securities in Unrealized Loss Positions | securities			2
Mortgage-backed securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	572,000	572,000
After 1 through 5 years	125,297,000	125,297,000
After 5 through 10 years	189,122,000	189,122,000
After ten years	0	0
Fair Value	314,991,000	314,991,000	$ 312,054,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	266,319,000	266,319,000	164,249,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4,099,000	4,099,000	841,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	5,878,000	5,878,000	20,011,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	270,000	270,000	611,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	272,197,000	272,197,000	184,260,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 4,369,000	$ 4,369,000	$ 1,452,000
Number of securities in Unrealized Loss Positions | securities	2	2	7
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	1,652,000	1,652,000
Fair Value	1,652,000	1,652,000	$ 1,906,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,652,000	1,652,000	1,906,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,398,000	1,398,000	1,224,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,652,000	1,652,000	1,906,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,398,000	$ 1,398,000	$ 1,224,000
Number of securities in Unrealized Loss Positions | securities	1	1	1
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	1,995,000	1,995,000
After 5 through 10 years	2,037,000	2,037,000
After ten years	144,000	144,000
Fair Value	4,176,000	4,176,000	$ 4,030,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	0	1,966,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0	34,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,995,000	1,995,000	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5,000	5,000	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,995,000	1,995,000	1,966,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 5,000	$ 5,000	$ 34,000

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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.

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Weighted average yield for available-for-sale investment securities held by the entity with maturities after ten years.

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Weighted average yield for available-for-sale investment securities held by the entity with maturities after one through five years.

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Weighted average yield for available-for-sale investment securities held by the entity with maturities after five through ten years.

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Weighted average yield for available-for-sale investment securities held by the entity with maturities of one year or less.

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The amount of other than temporary impairment losses on trust preferred securities which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

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Amount of the excess of amortized cost basis over fair value of preferred trust securities in a loss position.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
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