Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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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Discount rate from fair value on offering date that participants pay for shares.

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An excess of the fair value of the modified award over the fair value of the award immediately before the modification.

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Purchase price of common stock expressed as a percentage of its fair value.

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Stock-Based Awards - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested share-based awards	$ 105,000,000.0		$ 105,000,000.0
Unrecognized compensation cost related to unvested share-based awards, period for recognition			2 years 9 months 18 days
Share-based compensation expense	10,609,000	$ 4,107,000	$ 17,603,000	$ 10,336,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,300,000		$ 1,300,000
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent			85.00%
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date			15.00%
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period			6 months
President And Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense related to modification				$ 2,400,000
2017 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,608,183		1,608,183
Employee Stock Purchase Plan (ESPP)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,409,433		1,409,433