Debt (Details) $ in Millions	3 Months Ended	12 Months Ended
	Aug. 01, 2015 USD ($) CreditFacility	Jan. 31, 2015 USD ($) CreditFacility
Line of Credit Facility [Line Items]
Number of unsecured credit facilities | CreditFacility	2	2
Available borrowings under credit facilities	$ 80.0	$ 80.0
August 2014 Facility [Member]
Line of Credit Facility [Line Items]
Expiration date of renewed facility	Aug. 21, 2015	Aug. 21, 2015
Maximum borrowing capacity under renewed facility	$ 30.0	$ 30.0
Description of variable interest rate basis	Higher of prime, federal funds plus 0.5% or LIBOR	Higher of prime, federal funds plus 0.5% or LIBOR
Basis spread on variable interest rate (in hundredths)	0.50%	0.50%
Debt outstanding at period end	$ 0.0	$ 0.0
November 2014 Facility [Member]
Line of Credit Facility [Line Items]
Expiration date of renewed facility	Nov. 18, 2015	Nov. 18, 2015
Maximum borrowing capacity under renewed facility	$ 50.0	$ 50.0
Description of variable interest rate basis	prime	prime
Basis spread on variable interest rate (in hundredths)	2.00%	2.00%
Debt outstanding at period end	$ 0.0	$ 0.0