Income Taxes - Reconciliation of the Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (72,142)	$ (61,844)	$ (26,611)
State tax, net of federal benefit	152	44	32
Stock-based compensation expense	10,866	5,328	1,570
Research and development tax credits	(3,832)	(1,999)	(1,036)
Foreign rate differential	7,106	(429)	(194)
Change in valuation allowance	58,979	60,042	26,152
Other	440	195	378
Total provision for income taxes	$ 1,569	$ 1,337	$ 291