Liability Related to Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Millions	Dec. 30, 2020	Dec. 16, 2020	Feb. 24, 2012
2012 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights			$ 124.0
Transaction costs related to sale of potential future royalties			$ 4.4
2020 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights	$ 150.0
Transaction costs related to sale of potential future royalties	$ 3.8
Payment of transaction related to purchase and sale agreement		$ 210.0
Payment of transaction related to purchase and sale agreement if threshold is not achieved		240.0
Minimum transaction royalties payments needed to pay the difference between the 2025 threshold and 2020 transaction royalties		$ 208.0