Consolidated Statements of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Revenue	$ 807.0	$ 905.0	$ 858.0
Total revenue	819.5	928.2	887.4
Operating expenses:
Amortization of acquired intangibles	6.6	6.6	6.6
Total operating expenses	569.2	844.4	816.4
Operating income	250.3	83.8	71.0
Non-operating income and (expense):
Total non-operating income	7.7	51.4	71.0
Income from continuing operations before taxes	258.0	135.2	142.0
Income tax expense	18.0	5.0	132.8
Income from continuing operations	240.0	130.2	9.2
Gain (loss) on disposal of discontinued operations, net of tax	0.0	0.1	(0.1)
Net income	240.0	130.3	9.1
Net income attributable to controlling interests	$ 223.9	$ 136.4	$ 4.2
Earnings Per Share, Basic and Diluted [Abstract]
Earnings per share (basic) attributable to controlling interests (in dollars per share)	$ 2.45	$ 1.27	$ 0.04
Earnings per share (diluted) attributable to controlling interests (in dollars per share)	2.45	1.26	0.04
Continuing operations earnings per share (basic) attributable to controlling interests (in dollars per share)	2.45	1.27	0.04
Continuing operations earnings per share (diluted) attributable to controlling interests (in dollars per share)	$ 2.45	$ 1.26	$ 0.04
Weighted average shares outstanding (in shares)	91,205,412	107,431,821	110,708,598
Weighted average diluted shares outstanding (in shares)	91,268,952	107,623,192	111,381,142
Consolidated Entity Excluding Consolidated Funds
Revenue:
Other revenue	$ 6.0	$ 9.6	$ 1.2
Operating expenses:
Compensation and benefits	416.2	696.4	682.8
General and administrative expense	128.8	126.0	112.9
Amortization of acquired intangibles	6.6	6.6	6.6
Depreciation and amortization	17.2	14.5	11.7
Non-operating income and (expense):
Investment income	16.8	66.5	27.4
Interest income	2.2	3.2	0.8
Interest expense	(32.2)	(24.9)	(24.5)
Revaluation of DTA deed	0.0	20.0	51.8
Net consolidated Funds’ investment gains (losses)	16.8	66.5	27.4
Gain (loss) on disposal of discontinued operations, net of tax	0.0	0.1	(0.1)
Consolidated Funds
Revenue:
Total revenue	6.6	3.8	1.7
Operating expenses:
Total operating expenses	0.4	0.9	2.4
Non-operating income and (expense):
Net consolidated Funds’ investment gains (losses)	20.9	(13.4)	15.5
Net income (loss) attributable to non-controlling interests in consolidated Funds	16.1	(6.1)	4.9
Management fees | Consolidated Entity Excluding Consolidated Funds
Revenue:
Revenue	807.0	905.0	858.0
Performance fees | Consolidated Entity Excluding Consolidated Funds
Revenue:
Revenue	$ (0.1)	$ 9.8	$ 26.5