Common Stock and Stockholders' Equity (Details) - $ / shares	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2015
Class Of Stock [Line Items]
Capital stock shares authorized			1,300,000,000
Common Stock, par value			$ 0.0001
Preferred stock, shares authorized	100,000,000	100,000,000	100,000,000
Preferred stock, par value	$ 0.0001	$ 0.0001	$ 0.0001
Common Stock, conversion features	Established that shares of our Class B common stock are voluntarily convertible into shares of our Class A common stock at the option of the holder, generally automatically convertible into shares of our Class A common stock upon transfer, and all outstanding shares of our Class B common stock will automatically convert into shares of our Class A common stock once the aggregate number of shares of our Class B common stock represents less than 5% of the then outstanding shares of Class A and Class B common stock
Treasury Stock, shares	3,052,953	3,052,953
Class A Common Stock
Class Of Stock [Line Items]
Common Stock, par value	$ 0.0001	$ 0.0001
Common Stock, shares authorized	1,000,000,000	1,000,000,000	1,000,000,000
Common stock, voting rights	1 vote per share
Class B Common Stock
Class Of Stock [Line Items]
Common Stock, par value	$ 0.0001	$ 0.0001
Common Stock, shares authorized	200,000,000	200,000,000	200,000,000
Common stock, voting rights	10 votes per share
Maximum percentage of outstanding shares of Class A and Class B common stock, for automatic conversion of shares of Class B common stock	5.00%