Investments - Summary of Available-for-sale Securities (Details) - USD ($) $ in Millions	Jul. 30, 2016	Jan. 30, 2016	Aug. 01, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 27.0	$ 27.5	$ 23.5
Unrealized gain (loss)	0.0	(0.7)	(0.3)
Fair Value	27.0	26.8	23.2
US Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Cost	8.7	9.2	9.2
Unrealized gain (loss)	(0.4)	(0.4)	(0.3)
Fair Value	8.3	8.8	8.9
US government agency securities
Schedule of Available-for-sale Securities [Line Items]
Cost	4.3	4.0	1.0
Unrealized gain (loss)	0.0	0.0	(0.1)
Fair Value	4.3	4.0	0.9
Corporate bonds and notes
Schedule of Available-for-sale Securities [Line Items]
Cost	10.5	10.8	9.9
Unrealized gain (loss)	0.3	0.0	0.0
Fair Value	10.8	10.8	9.9
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)	0.1
Fair Value	$ 3.6	$ 3.2	$ 3.5