Summary of Significant Accounting Policies Carrying Value of Goodwill, Intangible Assets, and Long-lived Assets (Details) - USD ($)	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Goodwill And Intangible Assets Disclosure
Indicators of goodwill impairment	no	no	no
Impairment charges for Goodwill	$ 0	$ 0	$ 0
Indicators of long-lived assets impairment	no	no	no
Impairment charges for long-lived assets	$ 0	$ 0	$ 0
Goodwill	606,842,000	599,929,000	$ 549,044,000
Intangible assets, net	37,446,000	45,577,000
Purchased Technology and In-Process Research and Development
Goodwill And Intangible Assets Disclosure
Intangible Assets, Gross (Excluding Goodwill)	158,102,000	155,124,000
Finite-Lived Intangible Assets, Accumulated Amortization	(138,375,000)	(131,143,000)
Intangible assets, net	19,727,000	23,981,000
Other Intangible Assets
Goodwill And Intangible Assets Disclosure
Intangible Assets, Gross (Excluding Goodwill)	105,162,000	100,384,000
Finite-Lived Intangible Assets, Accumulated Amortization	(87,443,000)	(78,788,000)
Intangible assets, net	$ 17,719,000	$ 21,596,000