Investments - Summary of Available-for-sale Securities (Details) - USD ($) $ in Millions	Apr. 30, 2016	Jan. 30, 2016	May. 02, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 27.1	$ 27.5	$ 23.1
Unrealized Gain (Loss)	(0.3)	(0.7)	(0.1)
Fair Value	26.8	26.8	23.0
US Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Cost	9.1	9.2	9.1
Unrealized Gain (Loss)	(0.3)	(0.4)	(0.1)
Fair Value	8.8	8.8	9.0
US government agency securities
Schedule of Available-for-sale Securities [Line Items]
Cost	3.4	4.0	0.6
Unrealized Gain (Loss)	(0.1)	0.0	(0.1)
Fair Value	3.3	4.0	0.5
Corporate bonds and notes
Schedule of Available-for-sale Securities [Line Items]
Cost	11.1	10.8	10.0
Unrealized Gain (Loss)	0.2	0.0	0.1
Fair Value	11.3	10.8	10.1
Corporate equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost	3.5	3.5	3.4
Unrealized Gain (Loss)	(0.1)	(0.3)	0.0
Fair Value	$ 3.4	$ 3.2	$ 3.4