Income Taxes - Significant Component of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 19,599	$ 13,347
Research and development credit carryforwards	13,133	7,567
Lease liability	18,666	0
Stock-based compensation expense	7,642	6,623
Excess tax basis in intangible assets	3,572	12,109
Accrued bonus	4,065	1,049
Deferred rent	0	529
Other deferred tax assets	3,944	1,858
Total deferred tax assets	70,621	43,082
Less: valuation allowance	883	1,673
Total net deferred tax asset	69,738	41,409
Deferred tax liabilities:
Excess book basis in intangible assets	(39,500)	(362)
Restructuring liability	(29,635)	(33,730)
Convertible debt	(22,839)	(7,283)
Right-of-use asset	(17,596)	0
Depreciation	(10,328)	(6,933)
Other deferred tax liabilities	(80)	(92)
Total deferred tax liabilities	(119,978)	(48,400)
Net deferred tax liabilities	$ (50,240)	$ (6,991)