Investments - Summary of Short term Investments (Details) $ in Thousands	Sep. 30, 2020 USD ($) investment
Investments, Debt and Equity Securities [Abstract]
Number of held-to-maturity investments held | investment	1
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 543,884
Gross Unrealized Gains	279
Gross Unrealized Losses	(43)
Total Fair Value	544,120
Within 1 year, Amortized Cost	514,535
After 1 year through 5 years, Amortized Cost	27,151
After 5 years through 10 Years, Amortized Cost	2,198
Within 1 year, Fair Value	514,748
After 1 year through 5 years, Fair Value	27,172
After 5 years through 10 years, Fair Value	2,200
Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	351,359
Gross Unrealized Gains	252
Gross Unrealized Losses	(41)
Total Fair Value	351,570
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	32,283
Gross Unrealized Gains	32
Gross Unrealized Losses	(7)
Total Fair Value	32,308
Certificate of deposits
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,334
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	14,334
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	38,593
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	38,593
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	152,668
Gross Unrealized Gains	180
Gross Unrealized Losses	(31)
Total Fair Value	152,817
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	12,106
Gross Unrealized Gains	8
Gross Unrealized Losses	(1)
Total Fair Value	12,113
U.S. government agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	45,474
Gross Unrealized Gains	17
Gross Unrealized Losses	(2)
Total Fair Value	45,489
U.S. government bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	54,460
Gross Unrealized Gains	15
Gross Unrealized Losses	0
Total Fair Value	54,475
Variable rate demand notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	400
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	400
Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,041
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	1,041
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	192,525
Gross Unrealized Gains	27
Gross Unrealized Losses	(2)
Total Fair Value	192,550
Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	972
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	972
Certificate of deposits
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,303
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	3,303
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	8,000
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,856
Gross Unrealized Gains	27
Gross Unrealized Losses	(2)
Total Fair Value	13,881
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	161,837
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	161,837
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,557
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	4,557
Level 1
Debt Securities, Available-for-sale [Line Items]
Total	233,949
Level 1 | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	68,809
Level 1 | Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Certificate of deposits
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	14,334
Level 1 | Commercial paper
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | U.S. government agency bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | U.S. government bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	54,475
Level 1 | Variable rate demand notes
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	165,140
Level 1 | Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Certificate of deposits
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	3,303
Level 1 | Commercial paper
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 1 | Money market funds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	161,837
Level 1 | Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 2
Debt Securities, Available-for-sale [Line Items]
Total	310,171
Level 2 | Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	282,761
Level 2 | Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	32,308
Level 2 | Certificate of deposits
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 2 | Commercial paper
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	38,593
Level 2 | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	152,817
Level 2 | Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	12,113
Level 2 | U.S. government agency bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	45,489
Level 2 | U.S. government bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 2 | Variable rate demand notes
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	400
Level 2 | Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	1,041
Level 2 | Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	27,410
Level 2 | Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	972
Level 2 | Certificate of deposits
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 2 | Commercial paper
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	8,000
Level 2 | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	13,881
Level 2 | Money market funds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	0
Level 2 | Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Total Fair Value	$ 4,557