Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued in connection with employee stock purchase plan (in shares)	21,600,000
Restricted stock granted, weighted average fair value (in USD per share)	$ 59.19
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 28.8
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected weighted-average period of recognition for unrecognized compensation expense	2 years 2 months 12 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock granted, weighted average fair value (in USD per share)	$ 59.19	$ 48.45

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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