Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Liabilities:
Kolltan acquisition contingent consideration	$ 7,107	$ 8,267
Fair value | Level 3
Liabilities:
Kolltan acquisition contingent consideration	7,107	8,267
Fair Value Measurements. | Level 2
Assets:
Money market funds and cash equivalents	66,929	35,066
Marketable securities	350,905	150,586
Total financial assets at fair value	417,834	185,652
Fair Value Measurements. | Level 3
Liabilities:
Kolltan acquisition contingent consideration	7,107	8,267
Total financial liabilities at fair value	7,107	8,267
Fair Value Measurements. | Fair value
Assets:
Money market funds and cash equivalents	66,929	35,066
Marketable securities	350,905	150,586
Total financial assets at fair value	417,834	185,652
Liabilities:
Kolltan acquisition contingent consideration	7,107	8,267
Total financial liabilities at fair value	$ 7,107	$ 8,267