Income Taxes Tax Effects of Temporary Differences and Carryforwards on Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2016	Jan. 31, 2015
Deferred Tax Assets, Net [Abstract]
Reserves and allowances	$ 12,954	$ 11,188
Accrued expenses not currently deductible	12,446	21,475
Stock-based compensation expense	8,259	6,988
Net operating loss carryforwards	24,138	34,618
Tax credit carryforwards	87,443	74,235
Purchased technology and other intangible assets	4,219	3,047
Deferred revenue	4,541	2,002
Other, net	8,394	6,762
Total gross deferred tax assets	162,394	160,315
Less valuation allowance	(63,554)	(91,956)
Deferred tax assets	98,840	68,359
Deferred Tax Liabilities, Net [Abstract]
Intangible assets	(13,163)	(12,976)
Undistributed foreign earnings	(87,390)	(50,163)
Convertible debt	(6,322)	(8,918)
Deferred tax liabilities, property, plant and equipment	(1,715)	(997)
Deferred tax liabilities, gross	(108,590)	(73,054)
Deferred tax liabilities, net	$ (9,750)	$ (4,695)