Estimated Fair Values of Other Financial Instruments (Detail) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Long-term debt, including current portion, Carrying Amount	[1],[2]	$ 549,728	$ 564,401
Long-term debt, including current portion, Fair Value	[1],[2]	$ 427,482	$ 442,751

[1] Carrying amounts include aggregate unamortized debt discount and debt issuance costs.

[2] Includes the 5.75% Convertible Notes accounted for under the fair value option. Refer to Note 7.