Organization and summary of significant accoutning policies - Cash and Equivalents (Details) - USD ($) $ in Millions	Jan. 28, 2017	Jan. 30, 2016	Jan. 31, 2015	Feb. 01, 2014
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 98.7	$ 137.7	$ 193.6	$ 247.6
Cash and cash equivalents held in money markets and other accounts
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	65.6	100.4
Cash equivalents from third-party credit card issuers
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	31.1	35.4
Cash on hand
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 2.0	$ 1.9