Consolidation - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Variable Interest Entities [Line Items]
Fee waivers	$ 130,500,000	$ 98,800,000
VIE
Variable Interest Entities [Line Items]
AUM	6,600,000,000		$ 9,600,000,000
VIE | Cash and Cash Equivalents
Variable Interest Entities [Line Items]
Maximum risk of loss from non-consolidated VIEs	72,200,000		111,900,000
VIE | Receivables - Affiliates
Variable Interest Entities [Line Items]
Maximum risk of loss from non-consolidated VIEs	22,400,000		$ 15,400,000
Financial Support, Fee Waivers
Variable Interest Entities [Line Items]
Money market funds which meet the scope exception of the consolidation guidance	100,100,000	68,100,000
Financial Support, Capital Contributions
Variable Interest Entities [Line Items]
Money market funds which meet the scope exception of the consolidation guidance	$ 0	$ 0