Investment Securities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Marketable Securities [Abstract]
Debt securities, AFS, accrued interest receivable	$ 12.4		$ 12.4
Carrying amount of equity investments without a readily determinable fair value	24.7		24.7		$ 25.6
Unrealized gain (loss) for equity investments with readily determinable fair values	$ 4.8	$ 1.2	$ (0.9)	$ 4.6