Consolidated Investment Products (CIP) - VIE Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	$ 404.1		$ 301.7	$ 284.1
Accounts receivable and other assets of CIP	488.3		175.5
Investments of CIP	8,304.8		7,910.0
Total assets	33,248.4		36,504.1
Debt of CIP	6,750.7		6,714.1
Other liabilities of CIP	1,118.6		588.6
Total liabilities	17,457.9		21,483.4
Total equity	15,426.6	$ 15,029.5	14,808.9	13,967.7	$ 13,942.4	$ 14,318.3
Total liabilities, temporary and permanent equity	33,248.4		$ 36,504.1
VIEs
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	7.7			9.1
Accounts receivable and other assets of CIP	3.4			1.2
Investments of CIP	242.9			114.2
Total assets	254.0			124.5
Debt of CIP	34.1			75.8
Other liabilities of CIP	206.2			37.8
Total liabilities	240.3			113.6
Total equity	13.7			10.9
Total liabilities, temporary and permanent equity	254.0			124.5
VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	0.0			0.0
Accounts receivable and other assets of CIP	1.0			0.0
Investments of CIP	131.4			0.0
Total assets	132.4			0.0
Debt of CIP	0.0			0.0
Other liabilities of CIP	1.0			0.0
Total liabilities	1.0			0.0
Total equity	131.4			0.0
Total liabilities, temporary and permanent equity	132.4			0.0
Deconsolidated VIEs
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	6.1			0.3
Accounts receivable and other assets of CIP	1.8			2.8
Investments of CIP	284.4			216.8
Total assets	292.3			219.9
Debt of CIP	258.3			0.0
Other liabilities of CIP	17.3			2.0
Total liabilities	275.6			2.0
Total equity	16.7			217.9
Total liabilities, temporary and permanent equity	292.3			219.9
Deconsolidated Voes's
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	0.1			0.2
Accounts receivable and other assets of CIP	0.1			1.1
Investments of CIP	27.6			134.1
Total assets	27.8			135.4
Debt of CIP	0.0			0.0
Other liabilities of CIP	0.0			0.0
Total liabilities	0.0			0.0
Total equity	27.8			135.4
Total liabilities, temporary and permanent equity	$ 27.8			$ 135.4