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Stockholders' Equity - RSUs and Revest Shares (Narrative) (Details)		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2020 cofounder shares	Dec. 31, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 35,713,000	$ 39,378,000	$ 100,856,000	$ 114,378,000
Signal Sciences Corp.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares restricted for stock awards (in shares) | shares						896,499
Number of cofounders with shares subject to revesting | cofounder						3
Shares held back for restricted stock awards, revesting period						2 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		28,700,000	27,800,000	$ 79,700,000	72,900,000
RSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				3 years
RSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
RSUs | First Year | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				3 years
Award vesting percentage				25.00%
RSUs | First Year | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Award vesting percentage				33.00%
RSUs | Remaining Period | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				24 months
RSUs | Remaining Period | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				36 months
Revest Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 0	7,300,000	$ 0	27,600,000
Nonvested shares sold that remain unvested (in shares) | shares							224,124
Proceeds from nonvested shares sold	$ 10,700,000
Modification expense, incremental fair value			$ 0		$ 5,600,000

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