Net Income (Loss) per Share - Additional Information (Detail)	Dec. 31, 2018 $ / shares
3.75% convertible senior notes due 2020, net of discount
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion price of convertible notes	$ 51.42

The price per share of the conversion feature embedded in the debt instrument.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant