License, Collaboration and Other Significant Agreements - Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Deferred Revenue:
Short-Term	$ 15,692	$ 15,214
Long-Term	27,965	$ 25,345
Total	43,657
Mitsubishi Tanabe Pharma Corporation | MTPC Agreement
Deferred Revenue:
Short-Term	4,883
Long-Term	0
Total	4,883
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement
Deferred Revenue:
Short-Term	6,308
Long-Term	16,664
Total	22,972
Otsuka Pharmaceutical Company. Ltd. | Otsuka International Agreement
Deferred Revenue:
Short-Term	4,501
Long-Term	6,623
Total	11,124
Vifor Pharma
Deferred Revenue:
Short-Term	0
Long-Term	4,678
Total	$ 4,678