Proceeds from Disgorgement of Stockholders' Short-Swing Profits

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Warrant Exercise Threshold, Percentage of Common Stock Owned

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Exercise price per share or per unit of warrants or rights outstanding.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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

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Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jan. 31, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued in transaction (shares)	2,415,000	1,854,838	3,162,500
Sale price of common stock (USD per share)	$ 97.00	$ 62.00	$ 38.85
Proceeds from sale of stock	$ 219,900	$ 107,900	$ 130,700
Exercise price of warrants (USD per share)			$ 0.001
Stock issued pursuant to stock option exercises (shares)				91,257	202,601	424,144	716,409
Proceeds from stock options exercised				$ 1,100	$ 2,200	$ 5,400	$ 9,500
Proceeds from disgorgement of stockholders' short-swing profits		$ 1,100				$ 1,050	$ 0
Note Warrant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued in transaction (shares)			421,650
Sale price of common stock (USD per share)			$ 38.849
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proportion of common stock owned (as a percent)							9.99%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proportion of common stock owned (as a percent)							4.99%