Segment Reporting (The impact of the Restatement segment) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Apr. 30, 2016	Jul. 31, 2017	Jul. 31, 2016	Jan. 31, 2017
Accounts Receivable - trade	$ 311.8	$ 261.1		$ 311.8	$ 261.1	$ 261.3
Inventories, net	1,398.1	1,386.9		1,398.1	1,386.9	1,381.4
Stockholders' equity	2,281.4	2,223.0		2,281.4	2,223.0	$ 2,221.1
Revenues	430.6	378.9		841.9	731.7
Cost of sales	312.0	286.4		610.4	555.7
Income tax expense	12.6	5.3		23.8	7.1
Net earnings	$ 20.7	$ 8.0		$ 39.1	$ 10.5
Basic net earnings per common share	$ 0.41	$ 0.15		$ 0.77	$ 0.20
Diluted net earnings per common share	$ 0.40	$ 0.15		$ 0.76	$ 0.20
Aerospace Solutions Group
Revenues	$ 357.1	$ 346.5		$ 704.6	$ 662.3
Application Of Accounting Principle [Member] | Aerospace Solutions Group
Revenues			$ (12.1)
Cost of sales			(6.6)
Net earnings			$ (3.4)
As Reported
Accounts Receivable - trade		289.0			289.0
Inventories, net		1,367.5			1,367.5
Stockholders' equity		2,228.3			2,228.3
Revenues		391.4			759.6
Cost of sales		296.3			575.0
Income tax expense		6.3			10.3
Net earnings		$ 9.6			$ 15.8
Basic net earnings per common share		$ 0.18			$ 0.30
Diluted net earnings per common share		$ 0.18			$ 0.30