The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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)(iii)

-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)(c), d(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 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)(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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 718

-SubTopic 10

-Section 50

-Paragraph 2

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

Reference 3: 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

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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- Definition

Weighted average remaining contractual term for option awards outstanding, 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 floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-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

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

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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Stock Incentive Plans (Details 2) (USD $)	12 Months Ended
Stock Incentive Plans (Details 2) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Exercise prices of outstanding options
Exercise prices of outstanding options, Number of options outstanding	2,117,110	2,093,108	1,830,397	2,194,286
Exercise prices of outstanding options, Average remaining contractual life	7 years 2 months 5 days
Exercise prices of outstanding options, Number of options exercisable	1,296,108
Range 1 [Member]
Exercise prices of outstanding options
Exercise prices of outstanding options, Lower range	0.78
Exercise prices of outstanding options, Upper range	4.94
Exercise prices of outstanding options, Number of options outstanding	561,170
Exercise prices of outstanding options, Average remaining contractual life	5 years 4 days
Exercise prices of outstanding options, Number of options exercisable	400,767
Range 2 [Member]
Exercise prices of outstanding options
Exercise prices of outstanding options, Lower range	7.75
Exercise prices of outstanding options, Upper range	9.58
Exercise prices of outstanding options, Number of options outstanding	322,989
Exercise prices of outstanding options, Average remaining contractual life	7 years 10 months 6 days
Exercise prices of outstanding options, Number of options exercisable	266,114
Range 3 [Member]
Exercise prices of outstanding options
Exercise prices of outstanding options, Lower range	10.02
Exercise prices of outstanding options, Upper range	14.00
Exercise prices of outstanding options, Number of options outstanding	386,617
Exercise prices of outstanding options, Average remaining contractual life	8 years 6 months 18 days
Exercise prices of outstanding options, Number of options exercisable	199,830
Range 4 [Member]
Exercise prices of outstanding options
Exercise prices of outstanding options, Lower range	14.57
Exercise prices of outstanding options, Upper range	18.80
Exercise prices of outstanding options, Number of options outstanding	75,854
Exercise prices of outstanding options, Average remaining contractual life	7 years 1 month 10 days
Exercise prices of outstanding options, Number of options exercisable	61,604
Range 5 [Member]
Exercise prices of outstanding options
Exercise prices of outstanding options, Lower range	19.21
Exercise prices of outstanding options, Upper range	22.92
Exercise prices of outstanding options, Number of options outstanding	557,625
Exercise prices of outstanding options, Average remaining contractual life	7 years 8 months 27 days
Exercise prices of outstanding options, Number of options exercisable	277,438
Range 6 [Member]
Exercise prices of outstanding options
Exercise prices of outstanding options, Lower range	24.95
Exercise prices of outstanding options, Upper range	32.67
Exercise prices of outstanding options, Number of options outstanding	212,855
Exercise prices of outstanding options, Average remaining contractual life	7 years 6 months 29 days
Exercise prices of outstanding options, Number of options exercisable	90,355