Segment Information - Noncontrolling Equity Interests in Distributable Earnings (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
General and administration
Segment Reporting Information [Line Items]
Purchase accounting and related adjustments	$ 8.7	$ 12.0	$ 55.2
Corporate and Reconciling Items
Segment Reporting Information [Line Items]
Purchase accounting and related adjustments	12.9	17.1	61.6
Corporate and Reconciling Items | General and administration
Segment Reporting Information [Line Items]
Amortization of recoupable portion of the purchase price	0.0	1.3	7.7
Noncontrolling interest discount amortization	0.0	0.0	13.2
Noncontrolling equity interest in distributable earnings	8.7	10.7	34.3
Purchase accounting and related adjustments	$ 8.7	$ 12.0	$ 55.2