Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets included in:
Total fair value	$ 1,191,079	$ 987,728
Liabilities included in:
Total fair value	0	138,102
Embedded Derivative Financial Instruments
Liabilities included in:
Total fair value	0	138,102
Money Market Funds
Assets included in:
Total fair value	1,191,079	987,728
Level 1
Assets included in:
Total fair value	1,191,079	987,728
Liabilities included in:
Total fair value	0	90,487
Level 1 | Embedded Derivative Financial Instruments
Liabilities included in:
Total fair value	0	90,487
Level 1 | Money Market Funds
Assets included in:
Total fair value	1,191,079	987,728
Level 2
Assets included in:
Total fair value	0	0
Liabilities included in:
Total fair value	0	0
Level 2 | Embedded Derivative Financial Instruments
Liabilities included in:
Total fair value	0	0
Level 2 | Money Market Funds
Assets included in:
Total fair value	0	0
Level 3
Assets included in:
Total fair value	0	0
Liabilities included in:
Total fair value	0	47,615
Level 3 | Embedded Derivative Financial Instruments
Liabilities included in:
Total fair value	0	47,615
Level 3 | Money Market Funds
Assets included in:
Total fair value	$ 0	$ 0