Furniture, Equipment and Leasehold Improvements, Net - Schedule of Furniture, Equipment and Leasehold Improvements (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Furniture, equipment and leasehold improvements [Abstract]
Furniture, equipment and leasehold improvements, gross	$ 400,900	$ 494,546
Less: Accumulated depreciation and amortization	(152,227)	(318,198)
Furniture, equipment and leasehold improvements, net	248,673	176,348
Gain (loss) on disposition of assets	3,100
New York City
Furniture, equipment and leasehold improvements [Abstract]
Gain (loss) on disposition of assets	201,800
Furniture and equipment
Furniture, equipment and leasehold improvements [Abstract]
Furniture, equipment and leasehold improvements, gross	151,478	168,415
Leasehold improvements
Furniture, equipment and leasehold improvements [Abstract]
Furniture, equipment and leasehold improvements, gross	$ 249,422	$ 326,131