Consolidated Statements Stockholders' Equity (USD $) In Thousands, except Share data	Total	Series A and B Convertible Preferred Stock [Member]	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, 2011	$ 9,173	$ 6,933		$ 326	$ 1,914
Beginning balance, shares at Jan. 31, 2011		85,000,000	21,899,083
Issuance of common stock upon exercise of stock options, value	6			6
Issuance of common stock upon exercise of stock options, shares	721,124		637,167
Issuance of common stock upon early exercise of stock options			83,957
Vesting of early exercised stock options	260			260
Stock-based compensation expense	434			434
Net income	4,230				4,230
Ending balance, value at Jan. 31, 2012	14,103	6,933		1,026	6,144
Ending balance, shares at Jan. 31, 2012		85,000,000	22,620,207
Issuance of common stock upon exercise of stock options, value	136			136
Issuance of common stock upon exercise of stock options, shares	2,237,707		1,481,017
Issuance of common stock upon early exercise of stock options			742,627
Vesting of early exercised stock options	224			224
Stock-based compensation expense	715			715
Other comprehensive income	5					5
Net income	18,783				18,783
Ending balance, value at Jan. 31, 2013	33,966	6,933		2,101	24,927	5
Ending balance, shares at Jan. 31, 2013		85,000,000	24,843,851
Issuance of common stock upon exercise of stock options, value	514			514
Issuance of common stock upon exercise of stock options, shares	3,274,694		2,913,194
Issuance of common stock upon early exercise of stock options			357,750
Vesting of early exercised stock options	572			572
Stock-based compensation expense	7,041			7,041
Conversion of preferred stock to common stock, value		(6,933)	1	6,932
Conversion of preferred stock to common stock, shares		(85,000,000)	85,000,000
Initial public offering, net of issuance costs, value	214,200			214,200
Initial public offering, net of issuance costs, shares			11,676,750
Excess tax benefits from stock-based compensation	174			174
Other comprehensive income	14					14
Net income	23,615				23,615
Ending balance, value at Jan. 31, 2014	$ 280,096		$ 1	$ 231,534	$ 48,542	$ 19
Ending balance, shares at Jan. 31, 2014			124,791,545