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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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Weighted average remaining contractual term for fully vested and expected to vest options that are exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Shareholder's Equity (Schedule of Stock Option Activity - Additional) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Total intrinsic value with options exercised	$ 2.6	$ 33.3	$ 6.3
Aggregate intrinsic value of options outstanding	3.6
Total intrinsic value of options vested or expected to vest	4.9
Vested or expected to vest at end of period, Number of Shares	158,721
Vested or expected to vest at end of period, weighted average exercise price (usd per share)
Vested or expected to vest at end of period, Weighted Average Remaining Contractual Life (in years)
Total Intrinsic value of options exercisable	$ 4.9
Exercisable at end of period, Number of Shares	158,721
Exercisable at end of period, Weighted Average Exercise Price (usd per share)
Exercisable at end of period, Weighted Average Remaining Contractual Life (in years)	1 year 292 days