Organization and summary of significant accoutning policies - Cash and Equivalents (Details) - USD ($) $ in Millions	Feb. 03, 2018	Jan. 28, 2017	Jan. 30, 2016	Jan. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 225.1	$ 98.7	$ 137.7	$ 193.6
Cash and cash equivalents held in money markets and other accounts
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	182.6	65.6
Cash equivalents from third-party credit card issuers
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	40.5	31.1
Cash on hand
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 2.0	$ 2.0