Goodwill and Other Intangible Assets - Goodwill Acquired (Details) - USD ($) $ in Millions		12 Months Ended
	Jul. 01, 2019	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Other Intangible Assets
Goodwill from acquisitions		$ 623.9	$ 113.9
Institutional Retirement & Trust business of Wells Fargo Bank
Goodwill and Other Intangible Assets
Purchase price of acquired business in the form of cash to be paid at the closing	$ 1,200.0
Maximum additional earn-out payment based upon retention of fee revenue	150.0
Goodwill from acquisitions	618.5
Customer relationships | Institutional Retirement & Trust business of Wells Fargo Bank
Goodwill and Other Intangible Assets
Finite lived intangible assets acquired	$ 510.3
Finite lived intangible asset, useful life	23 years
Technology | Institutional Retirement & Trust business of Wells Fargo Bank
Goodwill and Other Intangible Assets
Finite lived intangible assets acquired	$ 35.4
Finite lived intangible asset, useful life	6 years