The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1337-109256

Name:	us-gaap_EarningsPerShareBasicAndDiluted
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Revenue Recognition - Schedule of Revenue Impact of Adoption of ASC 606 on Net Loss Per Share (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net loss per share — basic and diluted	$ (0.40)	$ (0.60)	$ (1.47)	$ (1.82)
Guidance in Effect Prior Topic to ASC 606 [Member] \| Accounting Standards Update 2014-09 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net loss per share — basic and diluted	(0.52)		(1.68)
Impact of Adoption of ASC 606 [Member] \| Accounting Standards Update 2014-09 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net loss per share — basic and diluted	$ 0.12		$ 0.21