Assets Held for Sale Assets Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Long Lived Assets Held-for-sale [Line Items]
Long-lived asset impairment loss	$ 0	$ 87	$ 259	$ 87
Inventories	53,481	42,813	53,481	42,813	$ 42,336
Other current assets	3,910	2,747	3,910	2,747	2,689
Total current assets	153,837	131,427	153,837	131,427	138,816
Property, plant and equipment, net	105,651	108,948	105,651	108,948	106,324
Goodwill	46,752	40,703	46,752	40,703	40,649	$ 40,672
Amortizable intangible assets, net	11,375	12,511	11,375	12,511	12,048
Other assets	2,926	3,746	2,926	3,746	3,672
Total assets held for sale	320,541	297,335	320,541	297,335	301,509
Current liabilities	35,936	25,239	35,936	25,239	28,382
Other long-term liabilities	13,456	12,134	13,456	12,134	13,696
Aerostar [Member]
Long Lived Assets Held-for-sale [Line Items]
Goodwill	737	$ 789	737	$ 789	$ 789	$ 789
Aerostar [Member] | Client private and radar product assets [Member]
Long Lived Assets Held-for-sale [Line Items]
Inventories	3,000		3,000
Other current assets	79		79
Total current assets	3,079		3,079
Property, plant and equipment, net	227		227
Goodwill	102		102
Amortizable intangible assets, net	358		358
Other assets	17		17
Total assets held for sale	3,783		3,783
Current liabilities	392		392
Other long-term liabilities	127		127
Total liabilities held for sale	519		519
Operating Income (Loss) [Member] | Aerostar [Member] | Client private and radar product assets [Member]
Long Lived Assets Held-for-sale [Line Items]
Long-lived asset impairment loss	$ 0		$ 0