Investment Securities Held to Maturity (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	$ 305,175	$ 302,024	$ 317,632
Held-to-Maturity Securities, at Fair Value	312,500	308,566	322,335
Gross Unrealized Gains	7,451	6,705	5,316
Gross Unrealized Losses	126	163	613
Held-To-Maturity Securities, Pledged as Collateral	285,132	282,640	316,632
Maturities of Debt Securities at Amortized Cost
Within One Year	35,926
From 1 - 5 Years	132,842
From 5 - 10 Years	132,112
Over 10 Years	4,295
Maturities of Debt Securities, at Fair Value
Within One Year	35,968
From 1 - 5 Years	136,008
From 5 - 10 Years	136,153
Over 10 Years	4,371
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	0	6,724	62,745
12 Months or Longer	16,010	16,033	5,112
Total	16,010	22,757	67,857
Number of Securities in a Continuous Loss Position, in number of securities	592	75	103
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	0	25	572
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	126	138	41
Total	126	163	613
State and Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	195,951	188,472	190,847
Held-to-Maturity Securities, at Fair Value	200,578	193,252	195,524
Gross Unrealized Gains	4,753	4,935	5,042
Gross Unrealized Losses	126	155	365
Maturities of Debt Securities at Amortized Cost
Within One Year	35,926
From 1 - 5 Years	89,022
From 5 - 10 Years	67,708
Over 10 Years	3,295
Maturities of Debt Securities, at Fair Value
Within One Year	35,968
From 1 - 5 Years	91,192
From 5 - 10 Years	70,047
Over 10 Years	3,371
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	0	2,143	19,696
12 Months or Longer	16,010	16,033	5,112
Total	16,010	18,176	24,808
Number of Securities in a Continuous Loss Position, in number of securities	585	74	86
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	0	17	324
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	126	138	41
Total	126	155	365
Mortgage-Backed Securities - Residential [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	108,224	112,552	125,785
Held-to-Maturity Securities, at Fair Value	110,922	114,314	125,811
Gross Unrealized Gains	2,698	1,770	274
Gross Unrealized Losses	0	8	248
Maturities of Debt Securities at Amortized Cost
Within One Year	0
From 1 - 5 Years	43,820
From 5 - 10 Years	64,404
Over 10 Years	0
Maturities of Debt Securities, at Fair Value
Within One Year	0
From 1 - 5 Years	44,816
From 5 - 10 Years	66,106
Over 10 Years	0
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	0	4,581	43,049
12 Months or Longer	0	0	0
Total	0	4,581	43,049
Number of Securities in a Continuous Loss Position, in number of securities	7	1	17
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	0	8	248
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0	0
Total	0	8	248
Mortgage-Backed Securities - Residential [Member] | U.S. Government Agency Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	29,900	4,400	4,800
Held-to-Maturity Securities, at Fair Value	30,600	4,500	4,800
Mortgage-Backed Securities - Residential [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	78,300	108,100	121,000
Held-to-Maturity Securities, at Fair Value	80,300	109,800	121,000
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