Equity (Schedule of Stock Option Activity) (Details) - $ / shares	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Number of Options
Balance, beginning	3,330,953
Exercised	(17,402)	(35,769)
Forfeited	(187,859)
Balance, ending	3,125,692
Exercisable	1,408,599
Weighted Average Exercise Price
Balance, beginning	$ 31.53
Exercised	17.26
Forfeited	27.93
Balance, ending	31.83
Exercisable	$ 43.15

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.

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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.

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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.

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

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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- Definition

Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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- Definition

Number of share options (or share units) exercised during the current period.

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