Stock Compensation Plans (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 19,480	$ 3,760	$ 1,585
Dividend yield (as a percent)	0.00%
Cost of revenues
Stock-Based Compensation Expense
Total stock-based compensation expense	1,217	134	59
Research and development
Stock-Based Compensation Expense
Total stock-based compensation expense	6,170	841	347
Sales and marketing
Stock-Based Compensation Expense
Total stock-based compensation expense	8,093	1,488	495
General and administrative
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 4,000	$ 1,297	$ 684