Income Taxes Tax Effects of Temporary Differences and Carryforwards on Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2017	Jan. 31, 2016
Deferred Tax Assets, Net [Abstract]
Reserves and allowances	$ 10,346	$ 12,954
Accrued expenses not currently deductible	23,299	12,446
Stock-based compensation expense	8,403	8,259
Net operating loss carryforwards	14,743	24,138
Tax credit carryforwards	104,965	87,443
Purchased technology and other intangible assets	4,201	4,219
Deferred revenue	4,641	4,541
Other, net	8,845	8,394
Total gross deferred tax assets	179,443	162,394
Less valuation allowance	(74,041)	(63,554)
Deferred tax assets	105,402	98,840
Deferred Tax Liabilities, Net [Abstract]
Intangible assets	(14,002)	(13,163)
Undistributed foreign earnings	(97,696)	(87,390)
Convertible debt	(3,523)	(6,322)
Deferred tax liabilities, property, plant and equipment	(2,169)	(1,715)
Deferred tax liabilities, gross	(117,390)	(108,590)
Deferred tax liabilities, net	$ (11,988)	$ (9,750)