Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Net unrealized gains (losses) on equity securities in other income (expense)	$ 196.0	$ 118.3	$ (41.9)
Securities without readily determinable fair value	59.2	$ 55.6
Long-term debt fair value	$ 1,958.0