Investment Securities, Part II (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) securities	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) securities
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	$ 40,914
After 1 through 5 years	397,840
After 5 through 10 years	58,604
After ten years	3,219
Fair Value	$ 500,577		$ 518,848
Available-for-sale, Weighted Average Yield, Maturities Year One (in hundredths)	2.09%
Available-for-sale , Weighted Average Yield, Maturities After 1 through 5 Years (in hundredths)	2.34%
Available-for-sale, Weighted Average Yield, Maturities After 5 through 10 Years (in hundredths)	2.95%
Available-for-sale , Weighted Average Yield, Maturities After 10 Years (in hundredths)	1.96%
Available-for-sale , Weighted Average Yield, Maturities (in hundredths)	2.39%
Available-for-sale, Full Tax-equivalent Yield, Maturities Year One (in hundredths)	2.68%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 1 through 5 Years (in hundredths)	2.65%
Available-for-sale, Full Tax-equivalent Yield, Maturities After 5 through 10 years (in hundredths)	4.72%
Available-for-sale, Full Tax-equivalent Yield, Maturities After Ten Years (in hundredths)	2.58%
Available-for-sale, Full Tax-equivalent Yield, Maturities (in hundredths)	2.89%
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities	$ 112,161		85,208
Held To Maturity Weighted Average Yield Maturities Year One	1.75%
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	2.06%
Held To Maturity Weighted Average Yield Maturities After 10 Years	0.00%
Held To Maturity Weighted Average Yield Maturities	1.84%
Held To Maturity Tax Equivalent Yield Maturities Year One	1.75%
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	2.06%
Held To Maturity Tax Equivalent Yield Maturities After 10 Years	0.00%
Held To Maturity Tax Equivalent Yield Maturities	1.84%
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	$ 386,000		404,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	30,220		204,325
Less than 12 months, Unrealized Losses	(126)		(1,049)
12 months or longer, Fair Value	18,316		35,867
12 months or longer, Unrealized losses	(1,502)		(1,984)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	48,536		240,192
Total Unrealized Losses	$ 1,628		3,033
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	3,094
Market Value	1,746
Unrealized Gains (Losses)	(1,348)
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	29,992
After 1 through 5 years	20,218
After 5 through 10 years	0
After ten years	0
Fair Value	50,210		90,141
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	82,537
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	24,542
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	5,082
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	0
Held-to-maturity Securities	112,161		85,208
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	4,982		34,942
Less than 12 months, Unrealized Losses	(18)		(142)
12 months or longer, Fair Value	0		12,971
12 months or longer, Unrealized losses	0		(126)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,982		47,913
Total Unrealized Losses	18		$ 268
Number of securities in Unrealized Loss Positions | securities			6
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	24,504		$ 35,845
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(61)		(214)
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	24,504		35,845
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(61)		(214)
Obligations of states and political subdivisions
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	9,234
After 1 through 5 years	54,318
After 5 through 10 years	48,099
After ten years	1,390
Fair Value	113,041		110,717
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	0		3,168
Less than 12 months, Unrealized Losses	0		(32)
12 months or longer, Fair Value	0		979
12 months or longer, Unrealized losses	0		(23)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0		4,147
Total Unrealized Losses	0		$ 55
Number of securities in Unrealized Loss Positions | securities			2
Mortgage-backed securities: GSE residential
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less	1,688
After 1 through 5 years	319,311
After 5 through 10 years	10,505
After ten years	0
Fair Value	331,504		$ 312,054
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	23,259		164,249
Less than 12 months, Unrealized Losses	(87)		(841)
12 months or longer, Fair Value	16,570		20,011
12 months or longer, Unrealized losses	(154)		(611)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	39,829		184,260
Total Unrealized Losses	$ 241		$ 1,452
Number of securities in Unrealized Loss Positions | securities	6		7
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	1,746
Fair Value	1,746		$ 1,906
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	1,746		1,906
12 months or longer, Unrealized losses	(1,348)		(1,224)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,746		1,906
Total Unrealized Losses	$ 1,348		$ 1,224
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	3,993
After 5 through 10 years	0
After ten years	83
Fair Value	4,076		$ 4,030
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, Fair Value	1,979		1,966
Less than 12 months, Unrealized Losses	(21)		(34)
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	1,979		1,966
Total Unrealized Losses	$ 21		$ 34