Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) (USD $) In Thousands, except Per Share data	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010
Statement of Stockholders' Equity [Abstract]
Dividends declared per share	$ 0.48	$ 0.44
Income tax on unrealized gain on securities available for sale	$ 1,689	$ 979
Income tax on reclassification adjustment	8	5
Income tax on other comprehensive income	$ 1,697	$ 984

Aggregate dividends declared during the period for each share of common stock outstanding.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap
Data Type:	us-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax effect of the change in accumulated other comprehensive income, that is, the tax effect on items included in other comprehensive income during the period that is attributable to the parent entity.

+ References

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph c(3)

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 29, 30

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax effect on the reclassification adjustment for gains or losses realized upon the sale of securities during the period.

+ References

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph c(3)

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 25

+ Details

Name:	us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForSaleOfSecuritiesIncludedInNetIncomeTax
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Tax effect on gross appreciation or the gross loss in value of the total of unsold securities during the period being reported on.

+ References

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph c(3)

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 25

+ Details

Name:	us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_StatementOfStockholdersEquityAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration