Revenue (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Revenue, Major Customer [Line Items]
Total operating revenues	$ 1,598,900,000	$ 1,214,600,000
Deferred carried interest liabilities	57,900,000		$ 45,800,000	$ 61,300,000
Performance revenue recognized	0	5,900,000
Bermuda
Revenue, Major Customer [Line Items]
Total operating revenues	0	0
Americas
Revenue, Major Customer [Line Items]
Total operating revenues	1,180,700,000	760,000,000.0
UK
Revenue, Major Customer [Line Items]
Total operating revenues	170,800,000	210,700,000
EMEA ex UK (Europe, Middle East, and Africa)
Revenue, Major Customer [Line Items]
Total operating revenues	164,400,000	169,600,000
Asia
Revenue, Major Customer [Line Items]
Total operating revenues	$ 83,000,000.0	$ 74,300,000