Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 243,670	$ 140,769	$ 219,935
Research and development credit carryforwards	36,345	23,679	19,240
Orphan drug credit carryforwards	150,859	125,153	92,538
Accrued expenses and other	40,617	32,206	25,842
Deferred revenue	6,598	7,317	10,971
Deferred rent	24,798	19,308	26,196
Jublient license	448
Interest expense	29
Total gross deferred tax asset	503,364	348,432	394,722
Deferred tax liability
Depreciation	(5,157)	(5,451)	(4,474)
Right of use assets	(20,059)	(14,539)	(19,869)
UNICAP	(1,966)
Prepaid expenses	(2)
Valuation allowance	(476,180)	(328,442)	(370,379)
Net deferred tax asset	$ 0	$ 0	$ 0