Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill	$ 8,509,400,000	$ 7,157,100,000
Business combinations (See Note 2)	285,800,000	1,229,100,000
Foreign exchange	121,100,000	123,200,000
Goodwill	8,916,300,000	8,509,400,000
Goodwill impairment	0	0
Oppenheimer Funds Acquisition
Goodwill [Roll Forward]
Business combinations (See Note 2)	$ 285,800,000	$ 1,219,500,000