Marketable Securities - Additional Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) Security	Dec. 31, 2019 USD ($) Security
Marketable Securities [Abstract]
Number of available-for-sale debt securities, continuous unrealized loss position for less than 12 months | Security	60	0
Aggregate fair value of available-for-sale debt securities, continuous unrealized loss position for less than 12 months | $	$ 377,400,000
Number of available-for-sale debt securities, contractual maturity of less than 12 months | Security	42
Fair value of available-for-sale debt securities, contractual maturity of less than 12 months | $	$ 253,000,000
Number of available-for-sale debt securities, contractual maturity of greater than 12 months | Security	26
Fair value of available-for-sale debt securities, contractual maturity of greater than 12 months | $	$ 187,464,000
Sales of marketable securities | $	$ 0	$ 0
Number of securities decline in market value for in an unrealized loss position | Security	60