Long-term Debt - Net Carrying Amount of Equity Component of Convertible Debt (Detail) - 1.75% Convertible Senior Notes due 2021 [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2016
Debt Instrument [Line Items]
Net carrying amount			$ 32,900
Debt, Equity Component [Member]
Debt Instrument [Line Items]
Debt discount related to value of conversion option	$ 32,945	$ 32,945
Debt issuance cost	(1,179)	(1,179)
Net carrying amount	$ 31,766	$ 31,766

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Name:	us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant