NET INCOME PER SHARE - Tabular Disclosure (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic
Net income	$ 5,486	$ 16,251	$ 9,128	$ 18,616
Undistributed earnings allocated to participating securities	(148)	(72)	(215)	(79)
Net income attributable to common stockholders	$ 5,338	$ 16,179	$ 8,913	$ 18,537
Weighted average shares used in computing net income per share attributable to common stockholders - basic (in shares)	142,632	151,712	143,680	151,497
Net income per share attributable to common stockholders - basic (in dollars per share)	$ 0.04	$ 0.11	$ 0.06	$ 0.12
Diluted
Net income attributable to common stockholders	$ 5,338	$ 16,179	$ 8,913	$ 18,537
Effect of dilutive securities (in shares)	440	994	443	1,051
Weighted average shares used in computing net income per share attributable to common stockholders - diluted (in shares)	143,072	152,706	144,123	152,548
Net income per share attributable to common stockholders - diluted (in dollars per share)	$ 0.04	$ 0.11	$ 0.06	$ 0.12