Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Cash flows from operating activities:
Net income	$ 23.8	$ 15.7
Adjustments to reconcile net income (loss) attributable to redeemable non-controlling interests of consolidated Funds to net cash flows from operating activities of consolidated Funds:
Total net cash flows from operating activities	(48.8)	(40.4)
Cash flows from investing activities:
Net cash flows from investing activities	11.8	(1.4)
Cash flows from financing activities of consolidated Funds:
Net cash flows from financing activities	61.6	(2.6)
Effect of foreign exchange rate changes on cash and cash equivalents	0.1	(0.2)
Net increase (decrease) in cash and cash equivalents	24.7	(44.6)
Cash and cash equivalents at beginning of period	98.5	147.6
Cash and cash equivalents at end of period (including cash at consolidated Funds classified as restricted)	123.2	103.0
Supplemental disclosure of cash flow information:
Income taxes paid	1.4	1.4
Supplemental disclosure of non-cash financing transactions:
Payable for repurchases of common stock	1.6	0.0
Excise tax on repurchases of common stock	0.2	0.7
Consolidated Entity Excluding Consolidated Funds
Cash flows from operating activities:
Net income	23.8	15.7
Less: Net income attributable to redeemable non-controlling interests in consolidated Funds	(3.7)	(1.1)
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	4.2	4.6
Amortization of debt-related costs	1.1	1.1
Amortization and revaluation of non-cash compensation awards	0.8	6.2
Deferred income taxes	1.1	(2.7)
(Gains) on other investments	(0.1)	(4.4)
Changes in operating assets and liabilities:
Decrease in investment advisory fees receivable	32.7	24.4
Decrease in other receivables, prepayments, deposits and other assets	3.6	2.6
(Decrease) in accrued incentive compensation, operating lease liabilities and other liabilities	(101.6)	(72.1)
(Decrease) in accounts payable, accrued expenses and accrued income taxes	(10.6)	(13.6)
Adjustments to reconcile net income (loss) attributable to redeemable non-controlling interests of consolidated Funds to net cash flows from operating activities of consolidated Funds:
Total net cash flows from operating activities	(48.7)	(39.3)
Cash flows from investing activities:
Additions of fixed assets	(2.5)	(2.4)
Purchase of investment securities	(2.5)	(2.3)
Sale of investment securities	16.8	3.3
Cash flows from financing activities:
Proceeds from revolving credit facility	100.0	101.0
Repayment of revolving credit facility	(20.0)	(28.0)
Payment to OM plc for co-investment redemptions	0.0	(0.2)
Repurchase of common stock	(17.8)	(74.3)
Withholding tax payments related to stock option exercise and restricted stock vesting	(0.2)	(1.8)
Supplemental disclosure of cash flow information:
Interest paid (excluding consolidated Funds)	6.7	7.2
Consolidated Entity Excluding Consolidated Funds | Nonrelated Party
Cash flows from financing activities:
Dividends paid to stockholders	(0.2)	(0.3)
Consolidated Entity Excluding Consolidated Funds | Related Party
Cash flows from financing activities:
Dividends paid to stockholders	(0.2)	(0.1)
Consolidated Funds
Cash flows from operating activities:
Less: Net income attributable to redeemable non-controlling interests in consolidated Funds	3.7	1.1
Adjustments to reconcile net income to net cash flows from operating activities:
(Gains) on other investments	(2.7)	(0.8)
Adjustments to reconcile net income (loss) attributable to redeemable non-controlling interests of consolidated Funds to net cash flows from operating activities of consolidated Funds:
Purchase of investments	(71.7)	(18.8)
Sale of investments	73.4	17.0
(Increase) in receivables and other assets	(3.3)	(0.4)
Increase in accounts payable and other liabilities	0.5	0.8
Total net cash flows from operating activities	(0.1)	(1.1)
Cash flows from financing activities of consolidated Funds:
Redeemable non-controlling interest capital raised	$ 0.0	$ 1.1