Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Fair Value by Contractual Maturity (Details)

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Fair Value Measurements - Fair Value by Contractual Maturity (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less $ 75,692 $ 27,041
Over One Year Through Five Years 126,452 40,505
Over Five Years 0 0
Total 202,144 67,546
U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less 15,072 6,075
Over One Year Through Five Years 36,871 15,265
Over Five Years 0 0
Total 51,943 21,340
Yankee bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less 0  
Over One Year Through Five Years 3,058  
Over Five Years 0  
Total 3,058  
Agency bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less 14,091  
Over One Year Through Five Years 3,499  
Over Five Years 0  
Total 17,590  
Municipal bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less 0  
Over One Year Through Five Years 12,411  
Over Five Years 0  
Total 12,411  
Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less 21,964 14,543
Over One Year Through Five Years 0 0
Over Five Years 0 0
Total 21,964 14,543
Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less 16 560
Over One Year Through Five Years 26,588 13,978
Over Five Years 0 0
Total 26,604 14,538
Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
One Year or Less 24,549 5,863
Over One Year Through Five Years 44,025 11,262
Over Five Years 0 0
Total $ 68,574 $ 17,125