Summary of Significant Accounting Policies Carrying Value of Goodwill, Intangible Assets, and Long-lived Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
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	611,536	606,842	$ 599,929
Intangible assets, net	31,813	37,446
Purchased Technology and In-Process Research and Development
Goodwill And Intangible Assets Disclosure
Intangible Assets, Gross (Excluding Goodwill)	162,213	158,102
Finite-Lived Intangible Assets, Accumulated Amortization	(145,652)	(138,375)
Intangible assets, net	16,561	19,727
Other Intangible Assets
Goodwill And Intangible Assets Disclosure
Intangible Assets, Gross (Excluding Goodwill)	108,690	105,162
Finite-Lived Intangible Assets, Accumulated Amortization	(93,438)	(87,443)
Intangible assets, net	$ 15,252	$ 17,719