Marketable Securities and Fair Value Measurements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	May 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Marketable securities	$ 459,256,000	$ 0
Transfers between Level 1, Level 2 and Level 3	0	0
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Marketable securities	66,256,000
Certificates of deposit | Letter of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash balance held to secure letter of credit associated with lease	$ 1,500,000	$ 1,100,000	$ 1,100,000