Investments - Summary of Available-for-sale Securities (Details) - USD ($) $ in Millions	Oct. 29, 2016	Jan. 30, 2016	Oct. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 27.9	$ 27.5	$ 25.4
Unrealized gain (loss)	(0.4)	(0.7)	(0.4)
Fair Value	27.5	26.8	25.0
US Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Cost	8.8	9.2	9.2
Unrealized gain (loss)	(0.5)	(0.4)	(0.4)
Fair Value	8.3	8.8	8.8
US government agency securities
Schedule of Available-for-sale Securities [Line Items]
Cost	4.6	4.0	2.3
Unrealized gain (loss)	(0.1)	0.0	0.0
Fair Value	4.5	4.0	2.3
Corporate bonds and notes
Schedule of Available-for-sale Securities [Line Items]
Cost	11.0	10.8	10.5
Unrealized gain (loss)	0.1	0.0	0.0
Fair Value	11.1	10.8	10.5
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	$ 3.6	$ 3.2	$ 3.4