Income Taxes - Reconciliation of the Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (82,682)	$ (72,142)	$ (61,844)
State tax, net of federal benefit	276	152	44
Stock-based compensation expense	(5,242)	10,866	5,328
Research and development tax credits	(1,570)	(3,832)	(1,999)
Foreign rate differential	15,878	7,106	(429)
Change in valuation allowance	73,863	58,979	60,042
Other	1,364	440	195
Provision for income taxes	$ 1,887	$ 1,569	$ 1,337