Investment (Held-to-Maturity) Securities (Details) $ in Thousands		3 Months Ended
		Sep. 30, 2015 USD ($)		Dec. 31, 2014 USD ($)		Sep. 30, 2014 USD ($)
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 612,187		$ 651,745		$ 654,269
Investments Securities, Carrying Value		612,384	[1]	652,360	[2]	655,091	[3]
Investment securities, fair value		643,091		673,626		676,445
Investment Securities, Gross Unrealized Gain		30,951	[4]	22,874	[5]	22,522	[6]
Investment Securities, Gross Unrealized Loss		(244)	[6]	(1,608)	[5]	(1,168)	[6]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Net Carrying Value		612,384	[1]	652,360	[2]	655,091	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 643,091		673,626		676,445
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield		3.28%
Investment Securities, Pledged as Collateral [Abstract]
Investment Securities, Pledged as Collateral, Carrying Value		$ 50,380		63,495		66,470
Investment Securities, Pledged as Collateral, Fair Value		$ 52,249		$ 65,855		$ 69,031
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		32		162		107
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 7,533		$ 143,951		$ 25,854
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		18,015		60,837		62,553
Investment Securities, Continuous Unrealized Loss Position, Fair Value		25,548		204,788		88,407
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		145		1,063		929
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		99		545		239
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		244		1,608		1,168
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Carrying Value	[7]	28,653
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	[7]	30,080
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value		403,705
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value		428,024
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value		5,279
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value		5,313
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		174,747
Investment Securities, Portfolio Concentration Not Rated, Fair Value		179,674
Fixed Maturity Securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investments Securities, Carrying Value		583,731
Investment securities, fair value		613,011
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		63,326
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		318,514
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		104,011
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		97,880
Investment Securities, Debt Maturities, Net Carrying Value		583,731
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		63,604
Investment Securities, Debt Maturities, One to Five Years, Fair Value		323,712
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		115,494
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		110,201
Investment Securities, Debt Maturities, Fair Value		$ 613,011
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		1.91%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		2.16%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.24%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		5.90%
Investment Securities, Debt Maturities, Nominal Yield		3.31%
Investment Securities, Debt Maturities, Weighted Average Maturity	[8]	5.29
Municipal and other tax-exempt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 379,980		405,090		410,595
Investments Securities, Carrying Value		379,980	[1]	405,090	[2]	410,595	[3]
Investment securities, fair value		384,310		408,344		415,233
Investment Securities, Gross Unrealized Gain		4,461	[4]	4,205	[5]	4,847	[6]
Investment Securities, Gross Unrealized Loss		(131)	[6]	(951)	[5]	(209)	[6]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		51,529
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		276,168
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		18,225
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		34,058
Investment Securities, Debt Maturities, Net Carrying Value		379,980	[1]	405,090	[2]	410,595	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		51,641
Investment Securities, Debt Maturities, One to Five Years, Fair Value		278,013
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		18,406
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		36,250
Investment Securities, Debt Maturities, Fair Value		$ 384,310		$ 408,344		$ 415,233
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	[9]	1.41%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	[9]	1.78%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	[9]	3.18%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	[9]	5.77%
Investment Securities, Debt Maturities, Nominal Yield	[9]	2.16%
Investment Securities, Debt Maturities, Weighted Average Maturity	[8]	3.37
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		15		78		24
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 6,250		$ 112,677		$ 481
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		13,438		60,076		60,742
Investment Securities, Continuous Unrealized Loss Position, Fair Value		19,688		172,753		61,223
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		81		426		0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		50		525		209
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		131		951		209
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Carrying Value	[7]	0
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	[7]	0
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value		252,263
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value		253,734
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value		5,279
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value		5,313
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		122,438
Investment Securities, Portfolio Concentration Not Rated, Fair Value		125,263
Other debt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		203,751		211,520		205,911
Investments Securities, Carrying Value		203,751	[1]	211,520	[2]	205,911	[3]
Investment securities, fair value		228,701		227,819		220,953
Investment Securities, Gross Unrealized Gain		25,063	[4]	16,956	[5]	16,001	[6]
Investment Securities, Gross Unrealized Loss		(113)	[6]	(657)	[5]	(959)	[6]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		11,797
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		42,346
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		85,786
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		63,822
Investment Securities, Debt Maturities, Net Carrying Value		203,751	[1]	211,520	[2]	205,911	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		11,963
Investment Securities, Debt Maturities, One to Five Years, Fair Value		45,699
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		97,088
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		73,951
Investment Securities, Debt Maturities, Fair Value		$ 228,701		$ 227,819		$ 220,953
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		4.09%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		4.63%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.68%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		5.97%
Investment Securities, Debt Maturities, Nominal Yield		5.46%
Investment Securities, Debt Maturities, Weighted Average Maturity	[8]	8.89
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		17		84		83
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 1,283		$ 31,274		$ 25,373
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		4,577		761		1,811
Investment Securities, Continuous Unrealized Loss Position, Fair Value		5,860		32,035		27,184
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		64		637		929
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		49		20		30
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		113		657		959
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Carrying Value	[7]	0
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	[7]	0
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value		151,442
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value		174,290
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		52,309
Investment Securities, Portfolio Concentration Not Rated, Fair Value		54,411
U.S. agency residential mortgage-backed securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investments Securities, Carrying Value		28,653
Investment securities, fair value		30,080
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Net Carrying Value		28,653
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 30,080
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield	[10]	2.75%
Investment Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities		4 years
U.S. agency residential mortgage-backed securities [Member] | Other [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost		$ 28,456		35,135		37,763
Investments Securities, Carrying Value		28,653	[1]	35,750	[2]	38,585	[3]
Investment securities, fair value		30,080		37,463		40,259
Investment Securities, Gross Unrealized Gain		1,427	[4]	1,713	[5]	1,674	[6]
Investment Securities, Gross Unrealized Loss		0	[6]	0	[5]	0	[6]
Investments Securities, Transfers [Abstract]
Investment Securities, Transferred From Available For Sale Securities Portfolio, Net Unrealized Gain		197		615		822
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Net Carrying Value		28,653	[1]	35,750	[2]	38,585	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 30,080		$ 37,463		$ 40,259
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		0		0		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 0		$ 0		$ 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		0		0
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0		0		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		$ 0		$ 0
Other than Temporary Impairment Losses, Investment Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Lowest Current Credit Rating [Abstract]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Carrying Value	[7]	28,653
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	[7]	30,080
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value		0
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value		0
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		0
Investment Securities, Portfolio Concentration Not Rated, Fair Value		$ 0

[1] Carrying value includes $197 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 $615 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 $822 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] 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.

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

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

[10] 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.