Stock Based Compensation Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range (Details) (USD $)	12 Months Ended
Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding, Outstanding Options, in shares	442,385
Weighted-Average Remaining Contractual Life, Outstanding Options, in years	5 years 11 months 12 days
Weighted Average Exercise Price, Outstanding Options, in Weighted Average Exercise Price	$ 23.03
Number of Shares Outstanding, Exercisable Options, in shares	259,150
Weighted-Average Remaining Contractual Life, Exercisable Options, in years	4 years 5 months 12 days
Weighted-Average Exercise Price, Exercisable Options, in Weighted Average Exercise Price	$ 22.46
Exercise Price Range $19.47 to $20.27 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding, Outstanding Options, in shares	103,872
Weighted-Average Remaining Contractual Life, Outstanding Options, in years	5 years 7 months 28 days
Weighted Average Exercise Price, Outstanding Options, in Weighted Average Exercise Price	$ 19.99
Number of Shares Outstanding, Exercisable Options, in shares	86,021
Weighted-Average Remaining Contractual Life, Exercisable Options, in years	5 years 6 months 28 days
Weighted-Average Exercise Price, Exercisable Options, in Weighted Average Exercise Price	$ 19.93
Exercise Price Range $21.63 to $21.66 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding, Outstanding Options, in shares	32,719
Weighted-Average Remaining Contractual Life, Outstanding Options, in years	3 years 11 months 1 day
Weighted Average Exercise Price, Outstanding Options, in Weighted Average Exercise Price	$ 21.66
Number of Shares Outstanding, Exercisable Options, in shares	32,719
Weighted-Average Remaining Contractual Life, Exercisable Options, in years	3 years 11 months 1 day
Weighted-Average Exercise Price, Exercisable Options, in Weighted Average Exercise Price	$ 21.66
Exercise Price Range $22.19 to $22.71 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding, Outstanding Options, in shares	102,916
Weighted-Average Remaining Contractual Life, Outstanding Options, in years	5 years 2 months 29 days
Weighted Average Exercise Price, Outstanding Options, in Weighted Average Exercise Price	$ 22.56
Number of Shares Outstanding, Exercisable Options, in shares	66,826
Weighted-Average Remaining Contractual Life, Exercisable Options, in years	4 years 3 months 5 days
Weighted-Average Exercise Price, Exercisable Options, in Weighted Average Exercise Price	$ 22.47
Exercise Price Range $24.24 to $24.92 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding, Outstanding Options, in shares	148,676
Weighted-Average Remaining Contractual Life, Outstanding Options, in years	8 years 6 months 18 days
Weighted Average Exercise Price, Outstanding Options, in Weighted Average Exercise Price	$ 24.59
Number of Shares Outstanding, Exercisable Options, in shares	19,382
Weighted-Average Remaining Contractual Life, Exercisable Options, in years	8 years 0 months 2 days
Weighted-Average Exercise Price, Exercisable Options, in Weighted Average Exercise Price	$ 24.26
Exercise Price Range $26.29 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding, Outstanding Options, in shares	54,202
Weighted-Average Remaining Contractual Life, Outstanding Options, in years	1 year 11 months 15 days
Weighted Average Exercise Price, Outstanding Options, in Weighted Average Exercise Price	$ 26.29
Number of Shares Outstanding, Exercisable Options, in shares	54,202
Weighted-Average Remaining Contractual Life, Exercisable Options, in years	1 year 11 months 15 days
Weighted-Average Exercise Price, Exercisable Options, in Weighted Average Exercise Price	$ 26.29

Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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- Definition

Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

-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 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(a, 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.

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- Definition

The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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- Definition

Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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