NET INCOME PER SHARE - Tabular Disclosure (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic
Net income	$ 8,241	$ 7,807	$ 17,369	$ 26,423
Undistributed earnings allocated to participating securities	(273)	(36)	(464)	(115)
Net income attributable to common stockholders	$ 7,968	$ 7,771	$ 16,905	$ 26,308
Weighted average shares used in computing net income per share attributable to common stockholders - basic (in shares)	141,226	150,732	142,861	151,240
Net income per share attributable to common stockholders - basic (in dollars per share)	$ 0.06	$ 0.05	$ 0.12	$ 0.17
Diluted
Net income attributable to common stockholders	$ 7,968	$ 7,771	$ 16,905	$ 26,308
Effect of dilutive securities (in shares)	473	830	466	882
Weighted average shares used in computing net income per share attributable to common stockholders - diluted (in shares)	141,699	151,562	143,327	152,122
Net income per share attributable to common stockholders - diluted (in dollars per share)	$ 0.06	$ 0.05	$ 0.12	$ 0.17