Stock-Based Compensation (Details) (USD $)	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2010
Number of Stock Options
Outstanding at beginning of period, Number of Stock Options	28,825,986	28,129,885	28,129,885
Granted, Number of Stock Options
Exercised, Number of Stock Options	(624,058)
Forfeited, Number of Stock Options	(17,100)
Outstanding at end of period, Number of Stock Options	28,184,828	28,129,885	28,129,885
Weighted Average Exercise Price
Outstanding at beginning of year, Weighted Average Exercise Price	$ 12.77	$ 12.68	$ 12.68
Granted, Weighted Average Exercise Price
Exercised, Weighted Average Exercise Price	$ 5.51
Forfeited, Weighted Average Exercise Price	$ 9.50
Outstanding at end of year, Weighted Average Exercise Price	$ 12.93	$ 12.68	$ 12.68

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Share-based compensation arrangement by share-based payment award option exercises in period weighted average exercise price.

+ References

No definition available.

+ Details

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- Definition

Share-based compensation arrangement by share-based payment award option forfeitures in period weighted average exercise price.

+ References

No definition available.

+ Details

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- Definition

Share-based compensation arrangement by share-based payment award option grants in period weighted average exercise price.

+ References

No definition available.

+ Details

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- Definition

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 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)

+ Details

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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)

+ Details

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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)

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)(b)

+ Details

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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)

+ Details

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