Debt (Details) $ in Millions	3 Months Ended	12 Months Ended
	May 05, 2018 USD ($) CreditFacility	Feb. 03, 2018 USD ($) CreditFacility
Line of Credit Facility [Line Items]
Number of unsecured credit facilities | CreditFacility	2	2
Available borrowings under credit facilities	$ 60.0	$ 60.0
Days borrowings incurred against facilities	0 days	7 days
Average borrowings outstanding	$ 0.0	$ 4.1
Maximum borrowings outstanding	$ 0.0	$ 4.9
Average interest rate on outstanding borrowings	0.00%	2.78%
BOA Renewal of Line of Credit [Member]
Line of Credit Facility [Line Items]
Expiration date of renewed facility		Mar. 31, 2018
Maximum borrowing capacity under renewed facility		$ 30.0
Line of Credit Facility, Interest Rate Description		an interest rate agreed upon between the lender and us at the time a loan is made
Regions LOC [Member]
Line of Credit Facility [Line Items]
Expiration date of renewed facility	Apr. 30, 2019	Apr. 30, 2018
Maximum borrowing capacity under renewed facility	$ 30.0	$ 30.0
Line of Credit Facility, Interest Rate Description	one month LIBOR plus 2.0%	one month LIBOR plus 2.5%
Description of variable interest rate basis	one month LIBOR	one month LIBOR
Basis spread on variable interest rate (in hundredths)	2.00%	2.50%
Debt outstanding at period end	$ 0.0
Bank of America LOC [Member]
Line of Credit Facility [Line Items]
Expiration date of renewed facility	Apr. 30, 2019
Maximum borrowing capacity under renewed facility	$ 30.0
Line of Credit Facility, Interest Rate Description	an interest rate agreed upon between the lender and us at the time a loan is made
Debt outstanding at period end	$ 0.0