Cash Equivalents and Investments - Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) investment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Total investments In unrealized loss position | investment	69
OTTI, associated with credit losses	$ 0	$ 0	$ 0
Available for sale, debt securities, realized gains (losses)	0	0	0
Unrealized gains (losses), equity investments	0	$ 0	$ 0
Restricted cash and investments	67,200,000
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	29,000,000.0
Other long-term assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	$ 38,200,000