Stock-Based Compensation (Schedule of Option Share Awards) (Details) (USD $)	6 Months Ended
Jun. 30, 2011
Stock-Based Compensation
Shares outstanding, beginning balance	1,806,110
Granted
Forfeited
Expired
Exercised	(474,289)
Shares outstanding, ending balance	1,331,821
Weighted average exercise price, beginning of period	$ 30.96
Granted
Forfeited
Expired
Exercised	$ 28.94
Weighted average exercise price, end of period	$ 31.68
Weighted average remaining contractual term (in years)	2.4
Aggregate intrinsic value at end of period	$ 15,079

As of the balance sheet date, the total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of options outstanding.

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The decrease in the number of reserved shares that could potentially be issued attributable to the exercise or conversion during the reporting period of previously issued stock options under the option plan.

+ 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)(e)

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- Definition

The weighted average price at which option holders acquired shares when converting their stock options into shares under the plan during the reporting period.

+ 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)(e)

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- Definition

The decrease in the number of shares that could be issued attributable to the lapse of rights to exercise previously issued stock options under the terms of the option agreements under the plan during the reporting period.

+ 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)(g)

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The weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that lapsed during the reporting period.

+ 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)(g)

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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

+ 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)(f)

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- Definition

The weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated during the reporting period due to noncompliance with plan terms during the reporting period.

+ 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)(f)

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- Definition

The quantity of shares issuable on stock options awarded under the plan during the reporting period.

+ 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)(d)

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph c(1)

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- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance-sheet date, including vested options.

+ 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)(a)

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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph b(1)(b)

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- Definition

The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ 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)(a)

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- Definition

The weighted average period between the balance-sheet date and expiration for all awards outstanding under the plan, which may be expressed in a decimal value for number of years.

+ References

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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph a

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