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=96867065&loc=d3e5070-113901

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- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

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- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: 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=96867065&loc=d3e5070-113901

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)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Weighted average price 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 Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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Share-Based Compensation (Schedule Of Additional Selected Information On Stock Options) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding stock options, Number of shares	2,560,571	3,437,910	3,804,095	5,630,502
Outstanding stock options, Weighted average exercise price	$ 27.06	$ 26.44	$ 27.30	$ 31.60
Outstanding stock options, Weighted average remaining contractual life (years)	3 years 8 months 12 days
Exercisable stock options, Number of shares	1,648,367	1,892,136	2,187,259
Exercisable stock options, Weighted average exercise price	$ 26.55	$ 27.60	$ 26.35
Exercise Price Range $0.32 To $19.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding stock options, Number of shares	198,402
Outstanding stock options, Weighted average exercise price	$ 17.39
Outstanding stock options, Weighted average remaining contractual life (years)	1 year 5 months
Exercisable stock options, Number of shares	198,402
Exercisable stock options, Weighted average exercise price	$ 17.39
Exercise Price Range $20.00 To $24.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding stock options, Number of shares	744,058
Outstanding stock options, Weighted average exercise price	$ 21.50
Outstanding stock options, Weighted average remaining contractual life (years)	4 years 4 months
Exercisable stock options, Number of shares	276,953
Exercisable stock options, Weighted average exercise price	$ 22.33
Exercise Price Range $25.00 To $29.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding stock options, Number of shares	1,346,781
Outstanding stock options, Weighted average exercise price	$ 28.35
Outstanding stock options, Weighted average remaining contractual life (years)	3 years 6 months
Exercisable stock options, Number of shares	1,094,021
Exercisable stock options, Weighted average exercise price	$ 28.30
Exercise Price Range $30.00 To $39.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding stock options, Number of shares	32,191
Outstanding stock options, Weighted average exercise price	$ 30.10
Outstanding stock options, Weighted average remaining contractual life (years)	3 years 5 months
Exercisable stock options, Number of shares	32,191
Exercisable stock options, Weighted average exercise price	$ 30.10
Exercise Price Range Fourty Point Zero Zero To Fourty Four Point Nine Nine [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding stock options, Number of shares	192,339
Outstanding stock options, Weighted average exercise price	$ 44.17
Outstanding stock options, Weighted average remaining contractual life (years)	6 years 1 month
Exercisable stock options, Number of shares	0
Exercisable stock options, Weighted average exercise price	$ 0.00
Exercise Price Range $45.00 To $49.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding stock options, Number of shares	46,800
Outstanding stock options, Weighted average exercise price	$ 47.10
Outstanding stock options, Weighted average remaining contractual life (years)	3 months 24 days
Exercisable stock options, Number of shares	46,800
Exercisable stock options, Weighted average exercise price	$ 47.10