Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
Jan. 31, 2019	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued pursuant to stock option exercises (shares)		235,398	402,948
Proceeds from stock options exercised		$ 2.7	$ 5.9
Proceeds from disgrogement of short-swing profits	$ 1.1
IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued (shares)	1,854,838
Sale price of common stock (USD per share)	$ 62.00
Proceeds from sale of stock	$ 107.9

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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