Fair Value of Financial Assets and Liabilities (Details) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains, noninterest income	$ (146,000)		$ (392,000)	$ 142,000	$ 308,000
Total gains, noninterest expense	0		0	0	0
Recurring [Member] \| Marketable Equity Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0		211,000	0	211,000	211,000
Total recognized gains (losses) included in net income	0		0	0	0
Issues	0		0	0	0
Settlements	0		0	0	0
Ending balance	0		211,000	0	211,000
Total gains (losses) for the period included in net income attributable to the change in unrealized gains or losses related to assets still held at the reporting date	0		0	0	0
Recurring [Member] \| Mortgage Servicing Rights [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	3,222,000		2,503,000	2,364,000	2,282,000	2,282,000
Total recognized gains (losses) included in net income	10,000		(257,000)	656,000	(85,000)
Issues	206,000		170,000	768,000	510,000
Settlements	(133,000)		(135,000)	(483,000)	(426,000)
Ending balance	3,305,000		2,281,000	3,305,000	2,281,000
Total gains (losses) for the period included in net income attributable to the change in unrealized gains or losses related to assets still held at the reporting date	10,000		(257,000)	656,000	(85,000)
Recurring [Member] \| Fair Value [Member]
Available-for-sale securities [Abstract]
U.S. Treasury and government agencies	62,516,000	60,915,000		62,516,000		60,915,000
State and political subdivisions	118,365,000	113,221,000		118,365,000		113,221,000
U.S. government sponsored agency mortgage-backed securities	429,517,000	383,581,000		429,517,000		383,581,000
Marketable equity securities	53,518,000	45,626,000		53,518,000		45,626,000
Mortgage servicing rights	3,305,000	2,364,000		3,305,000		2,364,000
Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Available-for-sale securities [Abstract]
U.S. Treasury and government agencies	0	0		0		0
State and political subdivisions	0	0		0		0
U.S. government sponsored agency mortgage-backed securities	0	0		0		0
Marketable equity securities	53,518,000	45,626,000		53,518,000		45,626,000
Mortgage servicing rights	0	0		0		0
Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Available-for-sale securities [Abstract]
U.S. Treasury and government agencies	62,516,000	60,915,000		62,516,000		60,915,000
State and political subdivisions	118,365,000	113,221,000		118,365,000		113,221,000
U.S. government sponsored agency mortgage-backed securities	429,517,000	383,581,000		429,517,000		383,581,000
Marketable equity securities	0	0		0		0
Mortgage servicing rights	0	0		0		0
Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Available-for-sale securities [Abstract]
U.S. Treasury and government agencies	0	0		0		0
State and political subdivisions	0	0		0		0
U.S. government sponsored agency mortgage-backed securities	0	0		0		0
Marketable equity securities	0	0		0		0
Mortgage servicing rights	3,305,000	2,364,000		3,305,000		2,364,000
Nonrecurring [Member]
Impaired loan (collateral dependent) [Abstract]
Impaired loans, fair value adjustments	500,000	500,000	500,000	1,600,000	700,000	1,200,000
Other real estate owned [Abstract]
Other real estate /assets owned, fair value adjustment	200,000	1,800,000	600,000	2,000,000	900,000	2,700,000
Nonrecurring [Member] \| Fair Value [Member]
Assets measured-nonrecurring basis [Abstract]
Impaired loans (collateral dependent)	4,985,000	5,465,000		4,985,000		5,465,000
Other real estate /assets owned	10,375,000	13,892,000		10,375,000		13,892,000
Nonrecurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets measured-nonrecurring basis [Abstract]
Impaired loans (collateral dependent)	0	0		0		0
Other real estate /assets owned	0	0		0		0
Nonrecurring [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Assets measured-nonrecurring basis [Abstract]
Impaired loans (collateral dependent)	0	0		0		0
Other real estate /assets owned	0	0		0		0
Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Assets measured-nonrecurring basis [Abstract]
Impaired loans (collateral dependent)	4,985,000	5,465,000		4,985,000		5,465,000
Other real estate /assets owned	$ 10,375,000	$ 13,892,000		$ 10,375,000		$ 13,892,000

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The amount at which an asset could be bought or sold in a current transaction between willing parties, that is, other than in a forced or liquidation sale.

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No definition available.

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The amount at which an asset could be bought or sold in a current transaction between willing parties, that is, other than in a forced or liquidation sale.

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No definition available.

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This item represents the amount of the total change in unrealized (holding) gains or losses for the period which are included in the statement of income (or changes in net assets) in other expense. Such unrealized (holding) gains or losses relate to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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No definition available.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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This item represent fair value disclosure in U.S. government agency mortgage-backed securities, available-for-sale at fair value.

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No definition available.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 25

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6903542&loc=d3e32014-111567

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This item represents the amount of the total realized and unrealized gains or losses for the period which are included in the statement of income (or changes in net assets) in other income; the fair value of which assets was or is measured on a recurring basis using significant unobservable inputs (Level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

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- Definition

Issues that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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- Definition

Settlements that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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