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Stock-Based Compensation - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended
	May 31, 2021 $ / shares	Nov. 30, 2020 $ / shares	May 31, 2020 tranche shares	Mar. 31, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares	Mar. 31, 2024 USD ($) $ / shares shares
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				$ 27.05		$ 12.92
Stock based compensation not recognized, options				$ 48,800
Stock based compensation not recognized, period for recognition (in years)				2 years 3 months 18 days
Compensation expense				$ 37,757		$ 27,041
Granted (in shares) | shares				524,770
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercises in period, intrinsic value				$ 1,100		$ 600
Expected dividend yield				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 4 months 24 days
Stock based compensation not recognized, other than options				$ 241,400
Shares underlying unvested performance-based restricted stock units
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 3 months 18 days
Stock based compensation not recognized, other than options				$ 26,700
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
Compensation expense				$ 4,300		$ 1,400
Granted (in shares) | shares					219,161
Total market-based restricted stock units approved and granted (in shares) | shares				281,378
Shares underlying unvested performance-based restricted stock units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average derivative service period		7 months 6 days
Market-based stock unit vesting period		7 months 6 days
Shares underlying unvested performance-based restricted stock units | 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
MSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of tranches | tranche			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				$ 800
Compensation expense				$ 1,600		$ 1,400
Maximum employee subscription rate, ESPP				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
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

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