Investment Securities, Part II (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) securities	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 92,112
After 1 through 5 years	300,891
After 5 through 10 years	94,938
After ten years	2,615
Fair Value	$ 490,556		$ 377,856
Available-for-sale, Weighted Average Yield, Maturities Year One (in hundredths)	1.74%
Available-for-sale , Weighted Average Yield, Maturities After 1 through 5 Years (in hundredths)	2.39%
Available-for-sale, Weighted Average Yield, Maturities After 5 through 10 Years (in hundredths)	2.80%
Available-for-sale , Weighted Average Yield, Maturities After 10 Years (in hundredths)	1.46%
Available-for-sale , Weighted Average Yield, Maturities (in hundredths)	2.32%
Available-for-sale, Full Tax-equivalent Yield, Maturities Year One (in hundredths)	1.90%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 1 through 5 Years (in hundredths)	2.73%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 5 through 10 years (in hundredths)	3.90%
Available-for-sale, Full Tax-equivalent Yield, Maturities After Ten Years (in hundredths)	1.72%
Available-for-sale, Full Tax-equivalent Yield, Maturities (in hundredths)	2.73%
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities	$ 49,105		53,650
Held To Maturity Weighted Average Yield Maturities Year One	2.11%
Held To Maturity Weighted Average Yield Maturities After 1 Through 5 Years	2.11%
Held To Maturity Weighted Average Yield Maturities After 5 Through 10 Years	2.53%
Held To Maturity Weighted Average Yield Maturities After 10 Years	0.00%
Held To Maturity Weighted Average Yield Maturities	2.15%
Held To Maturity Tax Equivalent Yield Maturities Year One	2.11%
Held To Maturity Tax Equivalent Yield Maturities After 1 Through 5 Years	2.11%
Held To Maturity Tax Equivalent Yield Maturities After 5 Through 10 Years	2.53%
Held To Maturity Tax Equivalent Yield Maturities After 10 Years	0.00%
Held To Maturity Tax Equivalent Yield Maturities	2.15%
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	$ 363,000		330,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	52,846		30,440
Less than 12 months, Unrealized Losses	(294)		(224)
12 months or longer, Fair Value	53,284		119,022
12 months or longer, Unrealized losses	(1,694)		(5,156)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	106,130		149,462
Total Unrealized Losses	$ 1,988		5,380
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	$ 1,111
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	$ 1,111
PreTSL XXVIII [Member]
Details of Trust Preferred Securities [Abstract]
Book Value	3,167
Market Value	2,125
Unrealized Gains (Losses)	(1,042)
Other-than- temporary Impairment Recorded To-date	(1,111)
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	85,648
After 1 through 5 years	41,803
After 5 through 10 years	0
After ten years	0
Fair Value	127,451		99,957
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	29,647
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	14,585
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	4,873
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	0
Held-to-maturity Securities	49,105		53,650
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	22,215		7,289
Less than 12 months, Unrealized Losses	(31)		(46)
12 months or longer, Fair Value	28,973		75,030
12 months or longer, Unrealized losses	(125)		(1,312)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	51,188		82,319
Total Unrealized Losses	$ 156		$ 1,358
Number of securities in Unrealized Loss Positions | securities	6		16
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 4,994		$ 4,853
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(6)		(12)
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	4,994		4,853
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(6)		(12)
Obligations of states and political subdivisions
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	5,669
After 1 through 5 years	44,125
After 5 through 10 years	47,278
After ten years	429
Fair Value	97,501		78,084
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	10,444		3,586
Less than 12 months, Unrealized Losses	(145)		(19)
12 months or longer, Fair Value	1,185		4,416
12 months or longer, Unrealized losses	(62)		(94)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	11,629		8,002
Total Unrealized Losses	$ 207		$ 113
Number of securities in Unrealized Loss Positions | securities	2		10
Mortgage-backed securities: GSE residential
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 795
After 1 through 5 years	210,986
After 5 through 10 years	47,660
After ten years	0
Fair Value	259,441		$ 195,401
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	18,219		19,565
Less than 12 months, Unrealized Losses	(86)		(159)
12 months or longer, Fair Value	21,001		37,224
12 months or longer, Unrealized losses	(465)		(802)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	39,220		56,789
Total Unrealized Losses	$ 551		$ 961
Number of securities in Unrealized Loss Positions | securities	7		11
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	2,125
Fair Value	2,125		$ 364
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	2,125		364
12 months or longer, Unrealized losses	(1,042)		(2,936)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,125		364
Total Unrealized Losses	$ 1,042		$ 2,936
Number of securities in Unrealized Loss Positions | securities	1		1
Other securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 0
After 1 through 5 years	3,977
After 5 through 10 years	0
After ten years	61
Fair Value	4,038		$ 4,050
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	1,968		0
Less than 12 months, Unrealized Losses	(32)		0
12 months or longer, Fair Value	0		1,988
12 months or longer, Unrealized losses	0		(12)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,968		1,988
Total Unrealized Losses	$ 32		$ 12