Fair Value Measurements - Schedule of Financial Assets and Liabilities Subject to Fair Value Measurements on a Recurring Basis and the Level of Inputs Used (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Marketable investments	$ 515,806	$ 410,031
Equity investments	16,472	0
Liabilities:
Warrant liabilities	44,825	343,400
U.S. Treasury
Assets:
Marketable investments	185,435	155,347
U.S. agency and government sponsored securities
Assets:
Marketable investments	4,991	19,996
Corporate bonds
Assets:
Marketable investments	84,729	45,450
Asset-backed securities
Assets:
Marketable investments	14,031	7,018
Fair Value, Recurring
Assets:
Total cash equivalents	118,390	198,292
Equity investments	16,472
Total marketable investments	445,755	276,710
Liabilities:
Warrant liabilities	44,825	343,400
Fair Value, Recurring | Public Warrants
Liabilities:
Warrant liabilities		228,933
Fair Value, Recurring | Private Warrants
Liabilities:
Warrant liabilities	44,825	114,467
Fair Value, Recurring | U.S. Treasury
Assets:
Marketable investments	185,435	130,348
Fair Value, Recurring | U.S. agency and government sponsored securities
Assets:
Marketable investments	4,991	19,996
Fair Value, Recurring | Commercial paper
Assets:
Marketable investments	140,097	73,898
Fair Value, Recurring | Corporate bonds
Assets:
Marketable investments	84,729	45,450
Fair Value, Recurring | Asset-backed securities
Assets:
Marketable investments	14,031	7,018
Fair Value, Recurring | Money market funds
Assets:
Total cash equivalents	31,867	64,971
Fair Value, Recurring | U.S. Treasury
Assets:
Total cash equivalents		24,999
Fair Value, Recurring | Commercial paper
Assets:
Total cash equivalents	86,523	108,322
Level 1 | Fair Value, Recurring
Assets:
Total cash equivalents	31,867	89,970
Equity investments	16,472
Total marketable investments	201,907	130,348
Liabilities:
Warrant liabilities	0	228,933
Level 1 | Fair Value, Recurring | Public Warrants
Liabilities:
Warrant liabilities		228,933
Level 1 | Fair Value, Recurring | Private Warrants
Liabilities:
Warrant liabilities	0	0
Level 1 | Fair Value, Recurring | U.S. Treasury
Assets:
Marketable investments	185,435	130,348
Level 1 | Fair Value, Recurring | U.S. agency and government sponsored securities
Assets:
Marketable investments	0	0
Level 1 | Fair Value, Recurring | Commercial paper
Assets:
Marketable investments	0	0
Level 1 | Fair Value, Recurring | Corporate bonds
Assets:
Marketable investments	0	0
Level 1 | Fair Value, Recurring | Asset-backed securities
Assets:
Marketable investments	0	0
Level 1 | Fair Value, Recurring | Money market funds
Assets:
Total cash equivalents	31,867	64,971
Level 1 | Fair Value, Recurring | U.S. Treasury
Assets:
Total cash equivalents		24,999
Level 1 | Fair Value, Recurring | Commercial paper
Assets:
Total cash equivalents	0	0
Level 2 | Fair Value, Recurring
Assets:
Total cash equivalents	86,523	108,322
Equity investments	0
Total marketable investments	243,848	146,362
Liabilities:
Warrant liabilities	0	114,467
Level 2 | Fair Value, Recurring | Public Warrants
Liabilities:
Warrant liabilities		0
Level 2 | Fair Value, Recurring | Private Warrants
Liabilities:
Warrant liabilities	0	114,467
Level 2 | Fair Value, Recurring | U.S. Treasury
Assets:
Marketable investments	0	0
Level 2 | Fair Value, Recurring | U.S. agency and government sponsored securities
Assets:
Marketable investments	4,991	19,996
Level 2 | Fair Value, Recurring | Commercial paper
Assets:
Marketable investments	140,097	73,898
Level 2 | Fair Value, Recurring | Corporate bonds
Assets:
Marketable investments	84,729	45,450
Level 2 | Fair Value, Recurring | Asset-backed securities
Assets:
Marketable investments	14,031	7,018
Level 2 | Fair Value, Recurring | Money market funds
Assets:
Total cash equivalents	0	0
Level 2 | Fair Value, Recurring | U.S. Treasury
Assets:
Total cash equivalents		0
Level 2 | Fair Value, Recurring | Commercial paper
Assets:
Total cash equivalents	86,523	108,322
Level 3 | Fair Value, Recurring
Assets:
Total cash equivalents	0	0
Equity investments	0
Total marketable investments	0	0
Liabilities:
Warrant liabilities	44,825	0
Level 3 | Fair Value, Recurring | Public Warrants
Liabilities:
Warrant liabilities		0
Level 3 | Fair Value, Recurring | Private Warrants
Liabilities:
Warrant liabilities	44,825	0
Level 3 | Fair Value, Recurring | U.S. Treasury
Assets:
Marketable investments	0	0
Level 3 | Fair Value, Recurring | U.S. agency and government sponsored securities
Assets:
Marketable investments	0	0
Level 3 | Fair Value, Recurring | Commercial paper
Assets:
Marketable investments	0	0
Level 3 | Fair Value, Recurring | Corporate bonds
Assets:
Marketable investments	0	0
Level 3 | Fair Value, Recurring | Asset-backed securities
Assets:
Marketable investments	0	0
Level 3 | Fair Value, Recurring | Money market funds
Assets:
Total cash equivalents	0	0
Level 3 | Fair Value, Recurring | U.S. Treasury
Assets:
Total cash equivalents		0
Level 3 | Fair Value, Recurring | Commercial paper
Assets:
Total cash equivalents	$ 0	$ 0