CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2016	Apr. 30, 2015
Cash flows from operating activities
Net loss	$ (100,896)	$ (71,186)
Adjustments to reconcile net loss to net cash provided by operating activities
Depreciation and amortization	6,461	3,466
Amortization of investment premiums	258	361
Stock-based compensation	91,370	66,109
Deferred income taxes	(506)	(319)
Excess tax benefit from employee stock plans	(692)	(466)
Changes in operating assets and liabilities, net of acquisitions
Accounts receivable, net	83,058	47,072
Prepaid expenses, other current and non-current assets	(8,119)	(327)
Accounts payable	99	402
Accrued payroll and compensation	(33,727)	(18,355)
Accrued expenses and other liabilities	(2,891)	640
Deferred revenue	1,274	1,218
Net cash provided by operating activities	35,689	28,615
Cash flows from investing activities
Purchases of investments	(142,787)	(160,514)
Maturities of investments	133,120	160,000
Purchases of property and equipment	(3,709)	(6,415)
Other investment activities	0	(1,500)
Net cash used in investing activities	(13,376)	(8,429)
Cash flows from financing activities
Proceeds from exercise of stock options	1,664	5,366
Taxes paid related to net share settlement of equity awards	(21,731)	0
Excess tax benefit from employee stock plans	692	466
Net cash provided (used in) by financing activities	(19,375)	5,832
Effect of exchange rate changes on cash and cash equivalents	766	174
Net increase in cash and cash equivalents	3,704	26,192
Cash and cash equivalents
Beginning of period	424,541	387,315
End of period	428,245	413,507
Supplemental disclosures
Cash paid for income taxes	990	489
Non-cash investing and financing activities
Change in accrued purchases of property and equipment	821	647
Vesting of early exercised options	0	28
Change in capitalized construction costs related to build-to-suit lease	$ 10,065	$ 8,508