Condensed Consolidated Statements of Stockholders Equity (USD $) In Thousands, except Share data	Total	Class A & B Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
Beginning balance, value at Jan. 31, 2014	$ 280,096	$ 1	$ 231,534	$ 48,542	$ 19
Beginning balance, shares at Jan. 31, 2014		124,791,545
Issuance of common stock upon exercise of stock options (unaudited) , value	2,212		2,212
Issuance of common stock upon exercise of stock options (unaudited) , shares	2,848,717	2,848,717
Vesting of early exercised stock options (unaudited)	231		231
Stock-based compensation expense (unaudited)	6,695		6,695
Issuance of common shares under Employee Stock Purchase Plan (unaudited), value	5,951		5,951
Issuance of common shares under Employee Stock Purchase Plan (unaudited), shares		350,059
Issuance of restricted stock units (unaudited), shares		29,292
Follow-on offering, net of issuance costs (unaudited) , value	34,495		34,495
Follow-on offering, net of issuance costs (unaudited) , shares		1,390,000
Excess tax benefits from employee stock plans (unaudited)	11,033		11,033
Other comprehensive income (unaudited)	(125)				(125)
Net income (unaudited)	16,799			16,799
Ending balance (unaudited), value at Jul. 31, 2014	$ 357,387	$ 1	$ 292,151	$ 65,341	$ (106)
Ending balance (unaudited), shares at Jul. 31, 2014		129,409,613