Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net income	$ 86.8	$ 67.1	$ 100.6
Adjustments to reconcile net income to net cash flows from operating activities:
Deferred income taxes	(10.2)	(6.0)	6.4
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	55.8	68.3	116.8
Cash flows from investing activities of consolidated Funds:
Net cash flows from investing activities	(50.1)	(43.9)	(13.0)
Cash flows from financing activities of consolidated Funds:
Net cash flows from financing activities	(54.4)	1.8	(233.7)
Effect of foreign exchange rate changes on cash and cash equivalents	(0.4)	0.2	(1.0)
Net increase (decrease) in cash and cash equivalents	(49.1)	26.4	(130.9)
Cash and cash equivalents at beginning of period (including restricted cash)	147.6	121.2	252.1
Cash and cash equivalents at end of period (including restricted cash)	98.5	147.6	121.2
Supplemental disclosure of cash flow information:
Income taxes paid	48.5	37.8	36.8
Supplemental disclosure of non-cash investing and financing transactions:
Excise tax on repurchases of common stock	0.7	0.0	0.0
Payable for repurchases of common stock	0.0	(1.8)	0.0
Deconsolidation of Funds	0.0	(1.9)	0.0
Consolidated Entity Excluding Consolidated Funds
Cash flows from operating activities:
Net income	86.8	67.1	100.6
Less: Net income attributable to redeemable non-controlling interests in consolidated Funds	(1.8)	(1.3)	0.0
Adjustments to reconcile net income to net cash flows from operating activities:
Amortization of acquired intangibles	0.0	0.0	0.1
Loss on extinguishment of debt	0.0	0.0	3.2
Depreciation and amortization	18.5	17.3	18.5
Amortization of debt-related costs	4.4	4.1	5.6
Amortization and revaluation of non-cash compensation awards	30.5	7.4	(30.3)
Deferred income taxes	(10.2)	(6.0)	6.4
(Gains) losses on other investments	(12.5)	(5.6)	3.4
Changes in operating assets and liabilities:
(Increase) decrease in investment advisory fees receivable	(21.3)	(20.9)	44.6
(Increase) decrease in other receivables, prepayments, deposits and other assets	0.6	0.2	(2.1)
Increase (decrease) in accrued incentive compensation, operating lease liabilities and other liabilities	15.1	10.2	(33.4)
Increase (decrease) in accounts payable, accrued expenses and accrued income taxes	(1.2)	5.2	2.4
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	108.9	77.7	119.0
Cash flows from investing activities:
Additions of fixed assets	(9.9)	(13.8)	(16.1)
Purchase of investment securities	(47.7)	(25.8)	(5.5)
Sale of investment securities	7.5	8.2	8.6
Cash flows from financing activities:
Proceeds from revolving credit facility	139.0	113.5	214.0
Repayment of third party borrowings and revolving credit facility	(139.0)	(113.5)	(339.0)
Payment of debt issuance costs	(0.7)	0.0	(0.9)
Proceeds from stock issuance	0.1	0.0	0.0
Payment to OM plc for co-investment redemptions	(0.2)	(0.4)	(1.1)
Withholding tax payments related to stock option exercise and restricted stock vesting	(11.4)	(2.4)	(2.3)
Supplemental disclosure of cash flow information:
Interest paid (excluding consolidated Funds)	15.0	15.5	16.0
Consolidated Entity Excluding Consolidated Funds | Nonrelated Party
Cash flows from financing activities:
Repurchases of common stock	(96.7)	(3.3)	(103.2)
Dividends paid to stockholders	(0.9)	(1.4)	(0.8)
Consolidated Entity Excluding Consolidated Funds | Related Party
Cash flows from financing activities:
Dividends paid to stockholders	(0.6)	(0.6)	(0.4)
Consolidated Funds
Cash flows from operating activities:
Less: Net income attributable to redeemable non-controlling interests in consolidated Funds	1.8	1.3	0.0
Adjustments to reconcile net income to net cash flows from operating activities:
(Gains) losses on other investments	0.4	(1.1)	0.0
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	(167.1)	(19.7)	(0.2)
Sale of investments	112.3	13.6	0.1
(Increase) decrease in receivables and other assets	(0.9)	(3.5)	(2.4)
Increase (decrease) in accounts payable and other liabilities	0.4	0.0	0.3
Total net cash flows from operating activities	(53.1)	(9.4)	(2.2)
Cash flows from investing activities of consolidated Funds:
Deconsolidation of Funds	0.0	(12.5)	0.0
Cash flows from financing activities of consolidated Funds:
Redeemable non-controlling interest capital raised	$ 56.0	$ 9.9	$ 0.0