Shareholders' equity - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Oct. 31, 2020	Aug. 01, 2020	May 02, 2020	Nov. 02, 2019	Aug. 03, 2019	May 04, 2019	Oct. 31, 2020	Nov. 02, 2019
Dividends Payable [Line Items]
Dividends declared per common share (usd per share)	$ 0.00	$ 0.00	$ 0.00	$ 0.37	$ 0.37	$ 0.37	$ 0.00	$ 1.11
Dividends, common stock	$ 0.0	$ 0.0	$ 0.0	$ 19.4	$ 19.3	$ 19.3	$ 0.0	$ 58.0
Dividends declared per preferred share (usd per share)	$ 12.81	$ 12.66	$ 12.50	$ 12.50	$ 12.50	$ 12.50	$ 37.97	$ 37.50
Dividends, preferred stock, paid-in-kind	$ 8.0	$ 7.9	$ 7.8	$ 7.8	$ 7.8	$ 7.8	$ 23.7	$ 23.4
Common Stock \| Accrued expenses and other current liabilities
Dividends Payable [Line Items]
Dividends payable				19.4				19.4
Series A Redeemable Convertible Preferred Stock \| Accrued expenses and other current liabilities
Dividends Payable [Line Items]
Dividends payable	$ 8.0			$ 7.8			$ 8.0	$ 7.8

Aggregate dividends declared during the period for each share of common stock outstanding.

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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
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-SubTopic 405
-Section 45
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Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of paid and unpaid preferred stock dividends declared with the form of settlement in payment-in-kind (PIK).

+ References

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Aggregate dividends declared during the period for each share of preferred stock outstanding.

+ References

No definition available.

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