Basis of Presentation and Summary of Significant Accounting Policies - Carrying Amounts and Fair Values of Company's Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market accounts	$ 115,769	$ 50,731
Marketable securities – certificates of deposit	67,637	116,469
Marketable securities – equity securities	58	70
Total	183,464	167,270
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market accounts	115,769	50,731
Marketable securities – certificates of deposit	67,637	116,469
Marketable securities – equity securities	58	70
Total	183,464	167,270
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market accounts	0	0
Marketable securities – certificates of deposit	0	0
Marketable securities – equity securities	0	0
Total	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market accounts	0	0
Marketable securities – certificates of deposit	0	0
Marketable securities – equity securities	0	0
Total	$ 0	$ 0