Summary of Significant Accounting Policies Carrying Value of Goodwill, Intangible Assets, and Long-lived Assets (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Goodwill And Intangible Assets Disclosure
Goodwill	$ 599,929	$ 549,044	$ 535,932
Intangible assets, net	45,577	22,799
Purchased Technology and In-Process Research and Development
Goodwill And Intangible Assets Disclosure
Intangible assets, net	23,981	11,210
Other Intangible Assets
Goodwill And Intangible Assets Disclosure
Intangible assets, net	$ 21,596	$ 11,589