Net Income Per Share - Reconciliation used in Computing Basic and Diluted Net Income (Loss) per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Income (loss) from continuing operations	$ (12,294)	$ (5,287)	$ (14,845)	$ (12,865)	$ (38,148)	$ 7,018	$ (6,205)	$ (2,695)	$ (45,291)	$ (40,030)	$ 2,858
Income from discontinued operations, net of tax	0	0	0	0	0	0	649	0	0	649	0
Net income (loss) used in computing basic net income (loss) per share	$ (12,294)	$ (5,287)	$ (14,845)	$ (12,865)	$ (38,148)	$ 7,018	$ (5,556)	$ (2,695)	$ (45,291)	$ (39,381)	$ 2,858
Denominator:
Shares used in computation of basic net income (loss) per share (weighted average common shares outstanding)	29,250	29,245	29,193	29,024	28,860	28,849	28,834	28,493	29,179	28,759	28,097
Dilutive potential common shares:
Stock options, ESPP, Restricted Stock and RSUs (in shares)									0	0	918
Shares used in computation of diluted net income (loss) per share (in shares)	29,250	29,245	29,193	29,024	28,860	29,298	28,834	28,493	29,179	28,759	29,015
Basic net income (loss) per share:
Basic net income (loss) per share - Continuing operations (in dollars per share)	$ (0.42)	$ (0.18)	$ (0.51)	$ (0.44)	$ (1.32)	$ 0.24	$ (0.22)	$ (0.09)	$ (1.55)	$ (1.39)	$ 0.10
Basic net income (loss) per share - Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.00	0.00	0.00	0.02	0.00	0.00	0.02	0.00
Basic net income per share (in dollars per share)	(0.42)	(0.18)	(0.51)	(0.44)	(1.32)	0.24	(0.20)	(0.09)	(1.55)	(1.37)	0.10
Diluted net income (loss) per share:
Diluted net income (loss) per share - Continuing operations (in dollars per share)	(0.42)	(0.18)	(0.51)	(0.44)	(1.32)	0.24	(0.22)	(0.09)	(1.55)	(1.39)	0.10
Diluted net income (loss) per share - Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.00	0.00	0.00	0.02	0.00	0.00	0.02	0.00
Diluted net income per share (in dollars per shares)	$ (0.42)	$ (0.18)	$ (0.51)	$ (0.44)	$ (1.32)	$ 0.24	$ (0.20)	$ (0.09)	$ (1.55)	$ (1.37)	$ 0.10