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Stock-Based Compensation - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended			9 Months Ended
	May 31, 2021 $ / shares	Nov. 30, 2020 $ / shares	May 31, 2020 tranche shares	Sep. 30, 2025 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares	Sep. 30, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares	Sep. 30, 2022 tranche
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value, grants in period (in usd per share) | $ / shares				$ 28.36		$ 19.42	$ 27.54	$ 15.35
Stock based compensation not recognized, options				$ 37,400			$ 37,400
Stock based compensation not recognized, period for recognition (in years)							1 year 10 months 24 days
Granted (in shares) | shares							632,803
Total stock-based compensation expense				42,808		$ 49,769	$ 123,027	$ 104,045
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercises in period, intrinsic value				$ 3,100		$ 100	$ 5,500	$ 9,100
Expected dividend yield				0.00%		0.00%	0.00%	0.00%
Shares underlying unvested restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation not recognized, period for recognition (in years)							2 years
Stock based compensation not recognized, other than options				$ 192,800			$ 192,800
Performance-based restricted stock units granted
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value, grants in period (in usd per share) | $ / shares		$ 113.40			$ 113.40
Stock based compensation not recognized, period for recognition (in years)							2 years
Stock based compensation not recognized, other than options				25,100			$ 25,100
Additional service period requirement		2 years
Weighted average grant date fair value, vested in period (in usd per share) | $ / shares	$ 148.19				$ 148.19
Cumulative charge					$ 24,800
Granted (in shares) | shares					219,161
Total stock-based compensation expense				4,900		$ 22,700	$ 12,700	$ 26,300
Total market-based restricted stock units approved and granted (in shares) | shares							281,378
Performance-based restricted stock units granted | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average derivative service period		1 year
Market-based stock unit vesting period		1 year
Performance-based restricted stock units granted | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average derivative service period		3 years
Market-based stock unit vesting period		3 years 1 month 6 days
Phantom Share Units (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average derivative service period	4 years	4 years
Market-based stock unit vesting period	6 months	6 months
MSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of tranches | tranche			3						3
Market-based restricted stock share price goal			30 days
MSUs | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total market-based restricted stock units approved and granted (in shares) | shares			1,695,574
Shares available for issuance under the 2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation not recognized, period for recognition (in years)							1 month 6 days
Stock based compensation not recognized, other than options				600			$ 600
Total stock-based compensation expense				$ 1,200		$ 900	$ 4,000	$ 3,400
Expected dividend yield				0.00%		0.00%	0.00%	0.00%
Maximum employee subscription rate, ESPP				10.00%			10.00%
Purchase price of common stock (as a percent of the fair value of common stock)							85.00%
Purchase period							6 months
Common stock issued under employee stock purchase plan (in shares) | shares				0		0	310,387	371,826

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