Fair Value of Financial Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Total assets	$ 105,163	$ 230,043
Liabilities:
Contingent value right liability	1,457
Total liabilities	15,857	14,190
Series B preferred shares forward contracts
Liabilities:
Derivative contracts	14,400	14,190
Money market funds
Assets:
Cash equivalents	3,616	6,858
U.S. corporate bonds
Assets:
Marketable securities	66,394	185,884
Foreign corporate bonds
Assets:
Marketable securities	35,153	37,301
Level 1
Assets:
Total assets	3,616	6,858
Liabilities:
Contingent value right liability	0
Total liabilities	0	0
Level 1 | Series B preferred shares forward contracts
Liabilities:
Derivative contracts	0	0
Level 1 | Money market funds
Assets:
Cash equivalents	3,616	6,858
Level 1 | U.S. corporate bonds
Assets:
Marketable securities	0	0
Level 1 | Foreign corporate bonds
Assets:
Marketable securities	0	0
Level 2
Assets:
Total assets	101,547	223,185
Liabilities:
Contingent value right liability	0
Total liabilities	0	0
Level 2 | Series B preferred shares forward contracts
Liabilities:
Derivative contracts	0	0
Level 2 | Money market funds
Assets:
Cash equivalents	0	0
Level 2 | U.S. corporate bonds
Assets:
Marketable securities	66,394	185,884
Level 2 | Foreign corporate bonds
Assets:
Marketable securities	35,153	37,301
Level 3
Assets:
Total assets	0	0
Liabilities:
Contingent value right liability	1,457
Total liabilities	15,857	14,190
Level 3 | Series B preferred shares forward contracts
Liabilities:
Derivative contracts	14,400	14,190
Level 3 | Money market funds
Assets:
Cash equivalents	0	0
Level 3 | U.S. corporate bonds
Assets:
Marketable securities	0	0
Level 3 | Foreign corporate bonds
Assets:
Marketable securities	$ 0	$ 0