Investment (Held-to-Maturity) Securities (Details) (USD $)	3 Months Ended
	Sep. 30, 2014		Dec. 31, 2013		Sep. 30, 2013		Sep. 30, 2011
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost	$ 654,269,000		$ 676,047,000		$ 641,901,000
Investments Securities, Carrying Value	655,091,000	[1]	677,878,000	[2]	644,225,000	[3]
Investment securities, fair value	676,445,000		687,127,000		654,479,000
Investment Securities, Gross Unrealized Gain	22,522,000	[4]	12,687,000	[4]	14,670,000	[4]
Investment Securities, Gross Unrealized Loss	(1,168,000)	[4]	(3,438,000)	[4]	(4,416,000)	[4]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Net Carrying Value	655,091,000	[1]	677,878,000	[2]	644,225,000	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair value	676,445,000		687,127,000		654,479,000
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield	3.25%
Investment Securities, Pledged as Collateral [Abstract]
Investment Securities, Pledged as Collateral, Carrying Value	66,470,000		89,087,000		92,442,000
Investment Securities, Pledged as Collateral, Fair Value	69,031,000		91,804,000		95,658,000
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	107		139		165
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	25,854,000		192,538,000		258,685,000
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	62,553,000		53,850,000		1,583,000
Investment Securities, Continuous Unrealized Loss Position, Fair Value	88,407,000		246,388,000		260,268,000
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	929,000		2,526,000		4,351,000
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	239,000		912,000		65,000
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	1,168,000		3,438,000		4,416,000
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	38,585,000	[5]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	40,259,000	[5]
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value	428,989,000
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value	445,976,000
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value	13,679,000
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value	13,865,000
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	173,838,000
Investment Securities, Portfolio Concentration Not Rated, Fair Value	176,345,000
Fixed Maturity Securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investments Securities, Carrying Value	616,506,000
Investment securities, fair value	636,186,000
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value	49,398,000
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value	345,343,000
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value	85,235,000
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value	136,530,000
Investment Securities, Debt Maturities, Net Carrying Value	616,506,000
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value	49,588,000
Investment Securities, Debt Maturities, One to Five Years, Fair Value	347,948,000
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value	88,421,000
Investment Securities, Debt Maturities, Over Ten Years, Fair Value	150,229,000
Investment Securities, Debt Maturities, Fair value	636,186,000
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	2.40%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	2.02%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	4.62%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	5.93%
Investment Securities, Debt Maturities, Nominal Yield	3.28%
Investment Securities, Debt Maturities, Weighted Average Maturity	5.82	[6]
Municipal and other tax-exempt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost	410,595,000		440,187,000		409,542,000
Investments Securities, Carrying Value	410,595,000	[1]	440,187,000	[2]	409,542,000	[3]
Investment securities, fair value	415,233,000		439,870,000		407,562,000
Investment Securities, Gross Unrealized Gain	4,847,000	[4]	2,452,000	[4]	2,316,000	[4]
Investment Securities, Gross Unrealized Loss	(209,000)	[4]	(2,769,000)	[4]	(4,296,000)	[4]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value	34,346,000
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value	308,611,000
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value	28,772,000
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value	38,866,000
Investment Securities, Debt Maturities, Net Carrying Value	410,595,000	[1]	440,187,000	[2]	409,542,000	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value	34,512,000
Investment Securities, Debt Maturities, One to Five Years, Fair Value	310,492,000
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value	29,280,000
Investment Securities, Debt Maturities, Over Ten Years, Fair Value	40,949,000
Investment Securities, Debt Maturities, Fair value	415,233,000		439,870,000		407,562,000
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	1.96%	[7]
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	1.68%	[7]
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	3.44%	[7]
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	5.36%	[7]
Investment Securities, Debt Maturities, Nominal Yield	2.18%	[7]
Investment Securities, Debt Maturities, Weighted Average Maturity	3.99	[6]
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	24		107		136
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	481,000		166,382,000		257,359,000
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	60,742,000		53,073,000		803,000
Investment Securities, Continuous Unrealized Loss Position, Fair Value	61,223,000		219,455,000		258,162,000
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0		1,921,000		4,292,000
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	209,000		848,000		4,000
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	209,000		2,769,000		4,296,000
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	0	[5]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	0	[5]
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value	268,636,000
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value	269,922,000
Investment Securities, Portfolio Concentration Rated A to BBB, Carrying Value	13,679,000
Investment Securities, Portfolio Concentration Rated A to BBB, Fair Value	13,865,000
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	128,280,000
Investment Securities, Portfolio Concentration Not Rated, Fair Value	131,446,000
Other debt securities [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost	205,911,000		187,509,000		178,501,000
Investments Securities, Carrying Value	205,911,000	[1]	187,509,000	[2]	178,501,000	[3]
Investment securities, fair value	220,953,000		195,393,000		188,475,000
Investment Securities, Gross Unrealized Gain	16,001,000	[4]	8,497,000	[4]	10,094,000	[4]
Investment Securities, Gross Unrealized Loss	(959,000)	[4]	(613,000)	[4]	(120,000)	[4]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value	15,052,000
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value	36,732,000
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value	56,463,000
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value	97,664,000
Investment Securities, Debt Maturities, Net Carrying Value	205,911,000	[1]	187,509,000	[2]	178,501,000	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value	15,076,000
Investment Securities, Debt Maturities, One to Five Years, Fair Value	37,456,000
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value	59,141,000
Investment Securities, Debt Maturities, Over Ten Years, Fair Value	109,280,000
Investment Securities, Debt Maturities, Fair value	220,953,000		195,393,000		188,475,000
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	3.41%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	4.91%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	5.22%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	6.16%
Investment Securities, Debt Maturities, Nominal Yield	5.48%
Investment Securities, Debt Maturities, Weighted Average Maturity	9.47	[6]
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	83		30		29
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	25,373,000		10,932,000		1,326,000
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,811,000		777,000		780,000
Investment Securities, Continuous Unrealized Loss Position, Fair Value	27,184,000		11,709,000		2,106,000
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	929,000		549,000		59,000
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	30,000		64,000		61,000
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss	959,000		613,000		120,000
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	0	[5]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	0	[5]
Investment Securities, Portfolio Concentration Rated AAA to AA, Carrying Value	160,353,000
Investment Securities, Portfolio Concentration Rated AAA to AA, Fair Value	176,054,000
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	45,558,000
Investment Securities, Portfolio Concentration Not Rated, Fair Value	44,899,000
U.S. agency residential mortgage-backed securities [Member] | Other [Member]
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investment Securities, Amortized Cost	37,763,000		48,351,000		53,858,000
Investments Securities, Carrying Value	38,585,000	[1]	50,182,000	[2]	56,182,000	[3]
Investment securities, fair value	40,259,000		51,864,000		58,442,000
Investment Securities, Gross Unrealized Gain	1,674,000	[4]	1,738,000	[4]	2,260,000	[4]
Investment Securities, Gross Unrealized Loss	0	[4]	(56,000)	[4]	0	[4]
Investments Securities, Transfers [Abstract]
Investment Securities, Transferred From Available For Sale Securities Portfolio, Fair Value							131,000,000
Investment Securities, Transferred From Available For Sale Securities Portfolio, Amortized Cost							118,000,000
Investment Securities, Transferred From Available For Sale Securities Portfolio, Net Unrealized Gain	822,000		1,800,000		2,300,000		13,000,000
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Net Carrying Value	38,585,000	[1]	50,182,000	[2]	56,182,000	[3]
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair value	40,259,000		51,864,000		58,442,000
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield	2.74%	[8]
Investment Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities	3 years 0 months
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	0		2		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0		15,224,000		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		15,224,000		0
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0		56,000		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		56,000		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	38,585,000	[5]
Investment Securities, Portfolio Concentration US Govt or GSE Securities Not Rated, Fair Value	40,259,000	[5]
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 $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 as discussed in greater detail following.

[2] Carrying value includes $1.8 million 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 as discussed in greater detail following.

[3] Carrying value includes $2.3 million 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 as discussed in greater detail following.

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

[5] 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.

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

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

[8] 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.