Significant Accounting Policies - Schedule of Computation of Basic and Diluted EPS (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net loss applicable to common stockholders	$ (29,497)	$ (42,854)
Denominator:
Weighted average common shares outstanding—basic and diluted	6,765,451	6,683,794
Net loss per share applicable to common stockholders—basic and diluted	$ (4.36)	$ (6.41)

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.

No definition available.

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