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Securities, Held to Maturity (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
--- | --- | ---
Held to maturity [Abstract] |  |
Amortized Cost | $ 160,539 | $ 143,995
Gross Unrealized Gains | 10,523 | 7,449
Gross Unrealized Losses | 216 | 15
Fair Value | 170,846 | 151,429
Amortized cost of single maturity securities held to maturity [Abstract] |  |
Due in one year or less | 3,907 |
Due after one year through five years | 8,537 |
Due after five years through ten years | 13,745 |
Due after ten years | 134,350 |
Amortized cost, total | 160,539 |
Fair value of single maturity securities held to maturity [Abstract] |  |
Due in one year or less | 3,958 |
Due after one year through five years | 8,814 |
Due after five years through ten years | 15,050 |
Due after ten years | 143,024 |
Fair value, total | 170,846 |
U.S. Government Agencies and Corporations [Member] |  |
Held to maturity [Abstract] |  |
Amortized Cost | 7,988 | 22,057
Gross Unrealized Gains | 563 | 562
Gross Unrealized Losses | 0 | 0
Fair Value | 8,551 | 22,619
State and Political Subdivisions [Member] |  |
Held to maturity [Abstract] |  |
Amortized Cost | 151,209 | 119,381
Gross Unrealized Gains | 9,880 | 6,775
Gross Unrealized Losses | 216 | 15
Fair Value | 160,873 | 126,141
Mortgage-Backed Securities [Member] |  |
Held to maturity [Abstract] |  |
Amortized Cost | 691 | 902
Gross Unrealized Gains | 73 | 94
Gross Unrealized Losses | 0 | 0
Fair Value | 764 | 996
Corporate Debt Securities [Member] |  |
Held to maturity [Abstract] |  |
Amortized Cost | 651 | 1,655
Gross Unrealized Gains | 7 | 18
Gross Unrealized Losses | 0 | 0
Fair Value | $ 658 | $ 1,673

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