Investment Securities Held to Maturity (Details) $ in Thousands	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	$ 317,480	$ 302,024	$ 296,522
Held-to-Maturity Securities, at Fair Value	324,009	308,566	302,567	$ 302,567
Gross Unrealized Gains	6,614	6,705	6,207
Gross Unrealized Losses	85	163	162
Held-To-Maturity Securities, Pledged as Collateral	296,921	282,640	277,636
Maturities of Debt Securities at Amortized Cost
Within One Year	37,916
From 1 - 5 Years	161,406
From 5 - 10 Years	112,603
Over 10 Years	5,556
Maturities of Debt Securities, at Fair Value
Within One Year	38,028
From 1 - 5 Years	165,429
From 5 - 10 Years	114,922
Over 10 Years	5,630
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	0	6,724	11,510
12 Months or Longer	14,896	16,033	17,424
Total	$ 14,896	$ 22,757	$ 28,934
Number of Securities in a Continuous Loss Position, in number of securities	51	75	63
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	$ 0	$ 25	$ 47
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	85	138	115
Total	85	163	162
State and Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	218,502	188,472	178,699
Held-to-Maturity Securities, at Fair Value	223,050	193,252	184,116
Gross Unrealized Gains	4,633	4,935	5,535
Gross Unrealized Losses	85	155	118
Maturities of Debt Securities at Amortized Cost
Within One Year	37,916
From 1 - 5 Years	88,502
From 5 - 10 Years	87,529
Over 10 Years	4,556
Maturities of Debt Securities, at Fair Value
Within One Year	38,028
From 1 - 5 Years	91,022
From 5 - 10 Years	89,370
Over 10 Years	4,630
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	0	2,143	2,289
12 Months or Longer	14,896	16,033	13,058
Total	$ 14,896	$ 18,176	$ 15,347
Number of Securities in a Continuous Loss Position, in number of securities	51	74	58
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	$ 0	$ 17	$ 15
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	85	138	103
Total	85	155	118
Mortgage-Backed Securities - Residential [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	97,978	112,552	116,823
Held-to-Maturity Securities, at Fair Value	99,959	114,314	117,451
Gross Unrealized Gains	1,981	1,770	672
Gross Unrealized Losses	0	8	44
Maturities of Debt Securities at Amortized Cost
Within One Year	0
From 1 - 5 Years	72,904
From 5 - 10 Years	25,074
Over 10 Years	0
Maturities of Debt Securities, at Fair Value
Within One Year	0
From 1 - 5 Years	74,407
From 5 - 10 Years	25,552
Over 10 Years	0
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	0	4,581	9,221
12 Months or Longer	0	0	4,366
Total	$ 0	$ 4,581	$ 13,587
Number of Securities in a Continuous Loss Position, in number of securities	0	1	5
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	$ 0	$ 8	$ 32
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	12
Total	0	8	44
Mortgage-Backed Securities - Residential [Member] | U.S. Government Agency Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	27,800	4,400	4,500
Held-to-Maturity Securities, at Fair Value	28,400	4,500	4,600
Mortgage-Backed Securities - Residential [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	70,200	108,100	112,300
Held-to-Maturity Securities, at Fair Value	71,500	109,800	112,900
Corporate and Other Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	1,000	1,000	1,000
Held-to-Maturity Securities, at Fair Value	1,000	1,000	1,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Maturities of Debt Securities at Amortized Cost
Within One Year	0
From 1 - 5 Years	0
From 5 - 10 Years	0
Over 10 Years	1,000
Maturities of Debt Securities, at Fair Value
Within One Year	0
From 1 - 5 Years	0
From 5 - 10 Years	0
Over 10 Years	1,000
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	0	0	0
12 Months or Longer	0	0	0
Total	$ 0	$ 0	$ 0
Number of Securities in a Continuous Loss Position, in number of securities	0	0	0
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	$ 0	$ 0	$ 0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	0
Total	$ 0	$ 0	$ 0