Summary of Significant Accounting Policies - Long-lived Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2018
Accounting Policies [Abstract]
Indefinite-lived intangible assets (excluding goodwill)	$ 34,100,000		$ 34,100,000
Impairment of long-lived assets held-for-use	$ 0	$ 0