Stock-Based Compensation - Employee Stock Option and Incentive Plan Activity Additional Information (Details) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021 USD ($) $ / shares	Jun. 30, 2021 USD ($) $ / shares
Additional information
Weighted average grant-date fair value (in dollars per share) \| $ / shares	$ 21.73	$ 21.71
Intrinsic value of options vested and expected to vest	$ 69.9	$ 69.9
Intrinsic value of options exercisable	26.0	26.0
Compensation cost not yet recognized	$ 36.0	$ 36.0
Weighted average period compensation cost is expected to be recognized (in years)		3 years 1 month 6 days

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 option under share-based payment arrangement.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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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