Investment Securities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Marketable Securities [Abstract]
Available-for-sale, accrued interest, after allowance for credit loss	$ 21.8		$ 21.8
Carrying amount of equity investments without a readily determinable fair value	55.2		55.2		$ 25.6
Unrealized gain (loss) for equity investments with readily determinable fair values	$ 1.2	$ 0.4	$ (3.6)	$ 4.9