Goodwill and Intangible Assets - Changes in Carrying Amounts of Goodwill (Details) $ in Thousands	6 Months Ended
	Jul. 31, 2016 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 329,703
Additions	0
Ending balance	329,703
Signal Integrity [Member]
Goodwill [Roll Forward]
Beginning balance	261,891
Additions	0
Ending balance	261,891
Power and High Reliability [Member]
Goodwill [Roll Forward]
Beginning balance	49,384
Additions	0
Ending balance	49,384
Wireless and Sensing [Member]
Goodwill [Roll Forward]
Beginning balance	18,428
Additions	0
Ending balance	$ 18,428