Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Cash flows from operating activities
Net income	$ 73,449	$ 44,310
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,438	3,596
Accretion of discount on short-term investments	(1,178)	(179)
Stock-based compensation	20,756	17,011
Amortization of deferred costs	4,849	4,519
Deferred income taxes	418	(50)
(Gain) Loss on foreign currency from mark-to-market derivative	(80)	23
Bad debt expense (recovery)	(153)	236
Changes in operating assets and liabilities:
Accounts receivable	139,510	69,592
Unbilled accounts receivable	(5,244)	(4,287)
Deferred costs	(4,601)	(3,551)
Income taxes	338	(2,496)
Prepaid expenses and other current and long-term assets	(2,759)	(713)
Accounts payable	(416)	1,981
Accrued expenses and other current liabilities	(759)	(2,564)
Deferred revenue	7,914	22,650
Lease liabilities	(1,629)
Other long-term liabilities	436	507
Net cash provided by operating activities	236,289	150,585
Cash flows from investing activities
Purchases of short-term investments	(228,894)	(193,162)
Maturities and sales of short-term investments	188,965	176,544
Purchases of property and equipment	(1,194)	(709)
Capitalized internal-use software development costs	(419)	(230)
Net cash used in investing activities	(41,542)	(17,557)
Cash flows from financing activities
Reduction of lease liabilities - finance leases	(249)
Proceeds from exercise of common stock options	3,391	7,839
Net cash provided by financing activities	3,142	7,839
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(702)	(811)
Net change in cash, cash equivalents, and restricted cash	197,187	140,056
Cash, cash equivalents, and restricted cash at beginning of period	552,178	321,387
Cash, cash equivalents, and restricted cash at end of period	749,365	461,443
Cash, cash equivalents, and restricted cash at end of period:
Cash and cash equivalents	748,158	460,239
Restricted cash included in other long-term assets	1,207	1,204
Cash, cash equivalents, and restricted cash at end of period	749,365	461,443
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds	2,383	4,116
Excess tax benefits from employee stock plans	13,552	9,679
Non-cash investing and financing activities:
Changes in accounts payable and accrued expenses related to property and equipment purchases	$ (634)	$ 99