Summary of Significant Accounting Policies - Revenue and Gross Accounts Receivable By Major Customer (Details) - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Percent of Total Gross Revenues | Fresenius Medical Care Rx
Concentration Risk [Line Items]
Concentration risk percentage	33.00%	29.00%	21.00%
Percent of Total Gross Revenues | AmerisourceBergen Drug Corporation
Concentration Risk [Line Items]
Concentration risk percentage	16.00%	12.00%	10.00%
Percent of Total Gross Revenues | Otsuka Pharmaceutical Co. Ltd.
Concentration Risk [Line Items]
Concentration risk percentage	14.00%	29.00%	45.00%
Percent of Total Gross Revenues | McKesson Corporation
Concentration Risk [Line Items]
Concentration risk percentage	13.00%	11.00%	0.00%
Percent of Total Gross Revenues | Cardinal Health, Inc.
Concentration Risk [Line Items]
Concentration risk percentage	11.00%	0.00%	0.00%
Percent of Gross Accounts Receivable | Fresenius Medical Care Rx
Concentration Risk [Line Items]
Concentration risk percentage	16.00%	19.00%
Percent of Gross Accounts Receivable | AmerisourceBergen Drug Corporation
Concentration Risk [Line Items]
Concentration risk percentage	15.00%	29.00%
Percent of Gross Accounts Receivable | Otsuka Pharmaceutical Co. Ltd.
Concentration Risk [Line Items]
Concentration risk percentage	22.00%	0.00%
Percent of Gross Accounts Receivable | McKesson Corporation
Concentration Risk [Line Items]
Concentration risk percentage	0.00%	12.00%
Percent of Gross Accounts Receivable | Cardinal Health, Inc.
Concentration Risk [Line Items]
Concentration risk percentage	10.00%	14.00%
Percent of Gross Accounts Receivable | MTPC
Concentration Risk [Line Items]
Concentration risk percentage	20.00%	0.00%