Equity-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 16, 2025	Dec. 06, 2025	Jun. 30, 2026	Apr. 30, 2026	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					$ 47,506	$ 6,901	$ 141,390	$ 136,460
Class A Common Stock | 2026 Acquisitions
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share issued (in shares)							963,285
Compensation expenses					1,800		$ 2,600
Vesting percentage							20.00%
Unamortized compensation cost not yet recognized					30,600		$ 30,600
Weighted-average period cost not yet recognized							4 years 7 months 6 days
Share based compensation, fair value assumptions grant date, amount							$ 33,300
Location, Statement of Income, Balance [Axis]: us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					43,076	0	125,468	104,512
Location, Statement of Income, Balance [Axis]: us-gaap:SellingGeneralAndAdministrativeExpense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					4,430	$ 6,901	$ 15,922	$ 31,948
Profits Interest Units (PIUs)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Granted, weighted average grant date fair value (in dollars per share)						$ 1,380.82		$ 766.54
Share issued (in shares)						5,000		178,025
Profits Interest Units (PIUs) | Location, Statement of Income, Balance [Axis]: us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses						$ 0		$ 104,500
Profits Interest Units (PIUs) | Location, Statement of Income, Balance [Axis]: us-gaap:SellingGeneralAndAdministrativeExpense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses						$ 6,900		$ 31,900
AT Umbrella LLC LTIP Units
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Granted, weighted average grant date fair value (in dollars per share)							$ 21.38
Share issued (in shares)				707,823
Compensation expenses					1,800		$ 4,500
Vesting percentage							20.00%
Unamortized compensation cost not yet recognized					28,300		$ 28,300
Weighted-average period cost not yet recognized							4 years 3 months 18 days
Annual anniversary of the vesting commencement							5 years
Issuance of threshold (in dollars per share)							$ 28.23		$ 16.00
AT Umbrella LLC LTIP Units | Location, Statement of Income, Balance [Axis]: us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					1,600		$ 3,900
Class X Aggregator Units
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Granted, weighted average grant date fair value (in dollars per share)							$ 16.00
Share issued (in shares)							0
Compensation expenses					40,400		$ 123,700
Vesting percentage							20.00%
Unamortized compensation cost not yet recognized					577,400		$ 577,400
Weighted-average period cost not yet recognized							4 years
Class X Aggregator Units | Location, Statement of Income, Balance [Axis]: us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					37,000		$ 110,700
Class X Aggregator Units | Location, Statement of Income, Balance [Axis]: us-gaap:SellingGeneralAndAdministrativeExpense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					$ 3,400		$ 13,100
2025 Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock reserved for issuance (in shares)					12,290,828		12,290,828
Shares outstanding percentage		5.00%
Annual shares authorized increase, percent of outstanding shares (in shares)		0
2025 Equity Incentive Plan | Restricted Stock Units (RSUs)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Granted, weighted average grant date fair value (in dollars per share)		$ 16.26
Share issued (in shares)	5,440,720		61,231
Compensation expenses					$ 3,500		$ 10,600
Vesting percentage							16.70%
Unamortized compensation cost not yet recognized					70,300		$ 70,300
Weighted-average period cost not yet recognized							5 years 2 months 12 days
2025 Equity Incentive Plan | Restricted Stock Units (RSUs) | Location, Statement of Income, Balance [Axis]: us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					2,800		$ 8,200
2025 Equity Incentive Plan | Restricted Stock Units (RSUs) | Location, Statement of Income, Balance [Axis]: us-gaap:SellingGeneralAndAdministrativeExpense
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expenses					$ 800		$ 2,300