Investment (Held-to-Maturity) Securities (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)		Mar. 31, 2015 USD ($)
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 576,004		$ 597,724		$ 634,151
Investments Securities, Carrying Value		576,047	[1]	597,836	[2]	634,587	[3]
Investment Securities, Fair Value		609,743		629,159		657,971
Investment Securities, Gross Unrealized Gain		33,828	[4]	31,687	[5]	24,651	[6]
Investment Securities, Gross Unrealized Loss		(132)	[6]	(364)	[5]	(1,267)	[6]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investments Securities, Debt Maturities, Carrying Value		576,047	[1]	597,836	[2]	634,587	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 609,743		629,159		657,971
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield		3.37%
Investment Securities, Pledged as Collateral [Abstract]
Investment Securities, Pledged as Collateral, Carrying Value		$ 263,720		231,033		63,425
Investment Securities, Pledged as Collateral, Fair Value		$ 268,422		$ 234,382		$ 65,723
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		26		85		134
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 14,175		$ 133,934		$ 72,499
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		6,240		15,095		56,140
Investment Securities, Continuous Unrealized Loss Position, Fair Value		20,415		149,029		128,639
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		8		270		1,019
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		124		95		248
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		132		365		1,267
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value		365,346
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value		390,765
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value		5,273
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value		5,294
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Carrying Value		0
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Fair Value		0
Investment Securities, Portfolio Concentration Not Rated, Carrying Value		205,428
Investment Securities, Portfolio Concentration Not Rated, Fair Value		213,684
Fixed Maturity Securities [Member]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		80,615
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		277,465
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		109,231
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		83,370
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		550,681
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		80,959
Investment Securities, Debt Maturities, One to Five Years, Fair Value		282,990
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		123,272
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		95,728
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		$ 582,949
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		1.79%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		2.38%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.24%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		5.94%
Investment Securities, Debt Maturities, Nominal Yield		3.40%
Investment Securities, Debt Maturities, Weighted Average Maturity	[7]	4.67
Municipal and other tax-exempt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 347,684		365,258		396,063
Investments Securities, Carrying Value		347,684	[1]	365,258	[2]	396,063	[3]
Investment Securities, Fair Value		352,542		368,910		400,112
Investment Securities, Gross Unrealized Gain		4,952	[4]	3,935	[5]	4,443	[6]
Investment Securities, Gross Unrealized Loss		(94)	[6]	(283)	[5]	(394)	[6]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		66,228
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		234,480
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		13,406
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		33,570
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		347,684
Investments Securities, Debt Maturities, Carrying Value		347,684	[1]	365,258	[2]	396,063	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		66,280
Investment Securities, Debt Maturities, One to Five Years, Fair Value		236,135
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		13,692
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		36,435
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		352,542
Investment Securities, Debt Maturities, Fair Value		$ 352,542		$ 368,910		$ 400,112
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	[8]	1.39%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	[8]	1.92%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	[8]	2.89%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	[8]	5.77%
Investment Securities, Debt Maturities, Nominal Yield	[8]	2.23%
Investment Securities, Debt Maturities, Weighted Average Maturity	[7]	3.14
Investment Securities,Debt Maturities, Effective tax rate for nominal yield calculation		39.00%
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		19		73		37
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 14,175		$ 127,319		$ 41,048
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		4,364		13,380		53,662
Investment Securities, Continuous Unrealized Loss Position, Fair Value		18,539		140,699		94,710
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		8		207		173
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		86		77		221
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		94		284		394
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value		225,162
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value		226,757
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value		5,273
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value		5,294
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Carrying Value		0
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Fair Value		0
Investment Securities, Portfolio Concentration Not Rated, Carrying Value		117,249
Investment Securities, Portfolio Concentration Not Rated, Fair Value		120,491
Other debt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		202,997		205,745		204,979
Investments Securities, Carrying Value		202,997	[1]	205,745	[2]	204,979	[3]
Investment Securities, Fair Value		230,407		232,375		222,606
Investment Securities, Gross Unrealized Gain		27,448	[4]	26,689	[5]	18,500	[6]
Investment Securities, Gross Unrealized Loss		(38)	[6]	(59)	[5]	(873)	[6]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		14,387
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		42,985
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		95,825
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		49,800
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		202,997
Investments Securities, Debt Maturities, Carrying Value		202,997	[1]	205,745	[2]	204,979	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		14,679
Investment Securities, Debt Maturities, One to Five Years, Fair Value		46,855
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		109,580
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		59,293
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		230,407
Investment Securities, Debt Maturities, Fair Value		$ 230,407		$ 232,375		$ 222,606
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		3.65%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		4.89%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.57%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		6.05%
Investment Securities, Debt Maturities, Nominal Yield		5.41%
Investment Securities, Debt Maturities, Weighted Average Maturity	[7]	7.31
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		7		11		97
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 0		$ 1,082		$ 31,451
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		1,876		1,715		2,478
Investment Securities, Continuous Unrealized Loss Position, Fair Value		1,876		2,797		33,929
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0		41		846
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		38		18		27
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		38		59		873
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value		140,184
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value		164,008
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value		0
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value		0
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Carrying Value		0
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Fair Value		0
Investment Securities, Portfolio Concentration Not Rated, Carrying Value		62,813
Investment Securities, Portfolio Concentration Not Rated, Fair Value		66,399
U.S. agency residential mortgage-backed securities [Member]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Net Carrying Value		25,366
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Fair Value		$ 26,794
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield	[9]	2.75%
Investment Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities		3 years 329 days
U.S. agency residential mortgage-backed securities [Member] | Other [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 25,323		26,721		33,109
Investments Securities, Carrying Value		25,366	[1],[10]	26,833	[2]	33,545	[3]
Investment Securities, Fair Value		26,794	[10]	27,874		35,253
Investment Securities, Gross Unrealized Gain		1,428	[4]	1,063	[5]	1,708	[6]
Investment Securities, Gross Unrealized Loss		0	[6]	(22)	[5]	0	[6]
Investments Securities, Transfers [Abstract]
Investment Securities, Transferred From Available For Sale Securities Portfolio, Net Unrealized Gain		43		112		436
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investments Securities, Debt Maturities, Carrying Value		25,366	[1],[10]	26,833	[2]	33,545	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 26,794	[10]	$ 27,874		$ 35,253
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		0		1		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 0		$ 5,533		$ 0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0		0		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value		0		5,533		0
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0		22		0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0		0		0
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		0		$ 22		$ 0
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value	[10]	0
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value	[10]	0
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value	[10]	0
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value	[10]	0
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Carrying Value	[10]	0
Investment Securities, Portfolio Concentration Rated Below Investment Grade, Fair Value	[10]	0
Investment Securities, Portfolio Concentration Not Rated, Carrying Value	[10]	25,366
Investment Securities, Portfolio Concentration Not Rated, Fair Value	[10]	$ 26,794

[1] Carrying value includes $43 thousand of net unrealized gain which remains in Accumulated other comprehensive income (“AOCI”) in the Consolidated Balance Sheets related to certain securities transferred from the Available for Sale securities portfolio to the Investment securities portfolio in 2011.

[2] Carrying value includes $112 thousand of net unrealized gain which remains in Accumulated other comprehensive income (“AOCI”) in the Consolidated Balance Sheets related to certain securities transferred from the Available for Sale securities portfolio to the Investment securities portfolio in 2011.

[3] Carrying value includes $436 thousand of net unrealized gain which remains in Accumulated other comprehensive income (“AOCI”) in the Consolidated Balance Sheets related to certain securities transferred from the Available for Sale securities portfolio to the Investment securities portfolio in 2011.

[4] Gross unrealized gains and losses are not recognized in AOCI in the Consolidated Balance Sheets.

[5] Gross unrealized gains and losses are not recognized in AOCI in the Consolidated Balance Sheets.

[6] Gross unrealized gains and losses are not recognized in AOCI in the Consolidated Balance Sheets.

[7] Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty.

[8] Calculated on a taxable equivalent basis using a 39% effective tax rate.

[9] The nominal yield on residential mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary - Unaudited for current yields on the investment securities portfolio.

[10] U.S. government and government sponsored enterprises are not rated by the nationally-recognized rating agencies as these securities are guaranteed by agencies of the U.S. government or government-sponsored enterprises.