Investment Securities Held to Maturity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	$ 248,914	$ 239,803	$ 252,902
Held-to-Maturity Securities, at Fair Value	252,691	248,252	261,574
Gross Unrealized Gains	4,841	8,512	8,707
Gross Unrealized Losses	1,064	63	35
Held-To-Maturity Securities, Pledged as Collateral	247,914	238,803	251,902
Maturities of Debt Securities at Amortized Cost
Within One Year	53,463
From 1 - 5 Years	123,391
From 5 - 10 Years	67,248
Over 10 Years	4,812
Maturities of Debt Securities, at Fair Value
Within One Year	53,490
From 1 - 5 Years	124,162
From 5 - 10 Years	70,091
Over 10 Years	4,948
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	82,411	21,583	14,908
12 Months or Longer	13,204	503	0
Total	95,615	22,086	14,908
Number of Securities in a Continuous Loss Position, in number of securities	199	61	34
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	915	62	35
12 Months or Longer	149	1	0
Total	1,064	63	35
State and Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	200,182	183,373	183,277
Held-to-Maturity Securities, at Fair Value	204,153	191,196	191,297
Gross Unrealized Gains	4,833	7,886	8,055
Gross Unrealized Losses	862	63	35
Maturities of Debt Securities at Amortized Cost
Within One Year	53,463
From 1 - 5 Years	75,659
From 5 - 10 Years	67,248
Over 10 Years	3,812
Maturities of Debt Securities, at Fair Value
Within One Year	53,490
From 1 - 5 Years	76,624
From 5 - 10 Years	70,091
Over 10 Years	3,948
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	39,598	21,583	14,908
12 Months or Longer	13,204	503	0
Total	52,802	22,086	14,908
Number of Securities in a Continuous Loss Position, in number of securities	172	61	34
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	712	62	35
12 Months or Longer	149	1	0
Total	861	63	35
Mortgage-Backed Securities - Residential [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	47,732	55,430	68,625
Held-to-Maturity Securities, at Fair Value	47,538	56,056	69,277
Gross Unrealized Gains	8	626	652
Gross Unrealized Losses	202	0	0
Maturities of Debt Securities at Amortized Cost
Within One Year	0
From 1 - 5 Years	47,732
From 5 - 10 Years	0
Over 10 Years	0
Maturities of Debt Securities, at Fair Value
Within One Year	0
From 1 - 5 Years	47,538
From 5 - 10 Years	0
Over 10 Years	0
Securities in a Continuous Loss Position, at Fair Value
Less than 12 Months	42,813	0	0
12 Months or Longer	0	0	0
Total	42,813	0	0
Number of Securities in a Continuous Loss Position, in number of securities	27	0	0
Unrealized Losses on Securities in a Continuous Loss Position
Less than 12 Months	203	0	0
12 Months or Longer	0	0	0
Total	203	0	0
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
12 Months or Longer	0	0	0
Total	0	0	0
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity	47,700		68,600
Held-to-Maturity Securities, at Fair Value	$ 47,500		$ 69,300