Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Accounting Policies [Abstract]
Cash equivalents						$ 0
Intangible assets, net	$ 39,811,000			$ 39,811,000		0
Required milestone payments capitalized to intangible asset				41,500,000
Intangible asset amortization	724,000			1,689,000
Reclassification from prepaid rent to operating right-of-use asset		$ 2,850,000
Restricted cash (included in other assets)	1,000,000			$ 1,000,000		$ 1,000,000
General payment terms, minimum				30 days
General payment terms, maximum				65 days
Expensed advertising costs	$ 33,086,000		$ 0	$ 72,601,000	$ 0