Shareholders' Equity (Narrative) (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
Mar. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized share-based compensation expense \| $	$ 49.7	$ 49.7
Recognized weighted average period		3 years 1 month
Shares of common stock exercised (in shares)		130,555
Intrinsic value of common stock exercised \| $		$ 2.4
Warrants outstanding (in shares)	93,013	93,013
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants awarded (in shares)	25,013	25,013
2013 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	668,442	668,442
Additional shares reserved for future issuance (in shares)		3,728,665
Public Stock Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock issued (in shares)	3,731,344
Price per share (usd per share) \| $ / shares	$ 33.50	$ 33.50
Gross proceeds \| $	$ 125.0
Proceeds, net of underwriting commissions \| $	117.5
Underwriting commissions \| $	$ 7.5

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Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.

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Number of warrants or rights outstanding.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested options awarded to employees as compensation.

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The cash outflow for cost incurred directly with the issuance of an equity security.

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Cash received on stock transaction after deduction of issuance costs.

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The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Number of additional shares authorized for issuance under an established share-based compensation plan.

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

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