Condensed consolidating financial information - Condensed consolidated statement of cash flows (Details) - USD ($) $ in Millions	9 Months Ended
	Oct. 28, 2017	Oct. 29, 2016
Cash flows from operating activities
Net cash provided by (used in) operating activities	$ 1,482.3	$ 360.9
Investing activities
Purchase of property, plant and equipment	(166.1)	(195.6)
Investment in subsidiaries		0.0
Purchase of available-for-sale securities	(1.7)	(10.4)
Proceeds from available-for-sale securities	0.9	10.0
Acquisition of R2Net Inc., net of cash acquired	(332.4)	0.0
Net cash used in investing activities	(499.3)	(196.0)
Financing activities
Dividends paid on common shares	(57.7)	(57.5)
Dividends paid on redeemable convertible preferred shares	(26.9)	0.0
Intra-entity dividends paid	0.0	0.0
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs	0.0	611.6
Proceeds from long-term debt	1,745.9	1,837.1
Proceeds from revolving credit facility	605.0	598.0
Repayments of revolving credit facility	(405.0)	(339.0)
Repurchase of common shares	(460.0)	(1,000.0)
Repayments of bank overdrafts	(5.9)	(13.3)
Other financing activities	(4.5)	(6.0)
Intra-entity activity, net	0.0	0.0
Net cash used in financing activities	(970.7)	(218.2)
Cash and cash equivalents at beginning of period	98.7	137.7
Decrease in cash and cash equivalents	12.3	(53.3)
Effect of exchange rate changes on cash and cash equivalents	2.4	(1.7)
Cash and cash equivalents at end of period	113.4	82.7
Consolidation, Eliminations
Cash flows from operating activities
Net cash provided by (used in) operating activities	(1,118.0)	(979.2)
Investing activities
Purchase of property, plant and equipment	0.0	0.0
Investment in subsidiaries		91.0
Purchase of available-for-sale securities	0.0	0.0
Proceeds from available-for-sale securities	0.0	0.0
Acquisition of R2Net Inc., net of cash acquired	0.0
Net cash used in investing activities	0.0	91.0
Financing activities
Dividends paid on common shares	0.0	0.0
Dividends paid on redeemable convertible preferred shares	0.0	0.0
Intra-entity dividends paid	1,118.0	979.2
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs		0.0
Proceeds from long-term debt	0.0	0.0
Proceeds from revolving credit facility	0.0	0.0
Repayments of revolving credit facility	0.0	0.0
Repurchase of common shares	0.0	0.0
Repayments of bank overdrafts	0.0
Other financing activities	0.0	(91.0)
Intra-entity activity, net	0.0	0.0
Net cash used in financing activities	1,118.0	888.2
Cash and cash equivalents at beginning of period	0.0	0.0
Decrease in cash and cash equivalents	0.0	0.0
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0
Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	1,467.2	385.1
Investing activities
Purchase of property, plant and equipment	(165.7)	(195.6)
Purchase of available-for-sale securities	0.0	0.0
Proceeds from available-for-sale securities	0.0	0.0
Acquisition of R2Net Inc., net of cash acquired	(332.4)
Net cash used in investing activities	(498.1)	(195.6)
Financing activities
Dividends paid on common shares	0.0	0.0
Dividends paid on redeemable convertible preferred shares	0.0	0.0
Intra-entity dividends paid	(800.0)	(650.0)
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs		0.0
Proceeds from long-term debt	0.0	0.0
Proceeds from revolving credit facility	605.0	598.0
Repayments of revolving credit facility	(405.0)	(339.0)
Repurchase of common shares	0.0	0.0
Repayments of bank overdrafts	(5.9)	(13.3)
Other financing activities	(1.4)	90.0
Intra-entity activity, net	(359.7)	91.6
Net cash used in financing activities	(982.7)	(234.7)
Cash and cash equivalents at beginning of period	70.3	102.0
Decrease in cash and cash equivalents	(13.6)	(45.2)
Effect of exchange rate changes on cash and cash equivalents	2.4	(1.1)
Cash and cash equivalents at end of period	59.1	55.7
Non-Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	511.4	391.4
Investing activities
Purchase of property, plant and equipment	(0.4)
Purchase of available-for-sale securities	(1.7)	(10.4)
Proceeds from available-for-sale securities	0.9	10.0
Net cash used in investing activities	(1.2)	(0.4)
Financing activities
Dividends paid on common shares	0.0	0.0
Dividends paid on redeemable convertible preferred shares	0.0	0.0
Intra-entity dividends paid	(318.0)	(329.2)
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs		0.0
Proceeds from long-term debt	1,745.9	1,837.1
Proceeds from revolving credit facility	0.0	0.0
Repayments of revolving credit facility	0.0	0.0
Repurchase of common shares	0.0	0.0
Repayments of bank overdrafts	0.0
Other financing activities	0.0	(0.6)
Intra-entity activity, net	435.0	(67.6)
Net cash used in financing activities	(483.0)	(397.4)
Cash and cash equivalents at beginning of period	26.6	33.7
Decrease in cash and cash equivalents	27.2	(6.4)
Effect of exchange rate changes on cash and cash equivalents		(0.6)
Cash and cash equivalents at end of period	53.8	26.7
Signet Jewelers Limited | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	617.1	558.7
Investing activities
Purchase of property, plant and equipment	0.0	0.0
Investment in subsidiaries		(91.0)
Purchase of available-for-sale securities	0.0	0.0
Proceeds from available-for-sale securities	0.0	0.0
Acquisition of R2Net Inc., net of cash acquired	0.0
Net cash used in investing activities	0.0	(91.0)
Financing activities
Dividends paid on common shares	(57.7)	(57.5)
Dividends paid on redeemable convertible preferred shares	(26.9)
Intra-entity dividends paid	0.0	0.0
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs		611.6
Proceeds from long-term debt	0.0	0.0
Proceeds from revolving credit facility	0.0	0.0
Repayments of revolving credit facility	0.0
Repurchase of common shares	(460.0)	(1,000.0)
Repayments of bank overdrafts	0.0
Other financing activities	(3.1)	(4.4)
Intra-entity activity, net	(70.7)	(19.1)
Net cash used in financing activities	(618.4)	(469.4)
Cash and cash equivalents at beginning of period	1.7	1.9
Decrease in cash and cash equivalents	(1.3)	(1.7)
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Cash and cash equivalents at end of period	0.4	0.2
Signet UK Finance plc | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	4.6	4.9
Investing activities
Purchase of property, plant and equipment	0.0	0.0
Investment in subsidiaries		0.0
Purchase of available-for-sale securities	0.0	0.0
Proceeds from available-for-sale securities	0.0	0.0
Acquisition of R2Net Inc., net of cash acquired	0.0
Net cash used in investing activities	0.0	0.0
Financing activities
Dividends paid on common shares	0.0	0.0
Dividends paid on redeemable convertible preferred shares	0.0	0.0
Intra-entity dividends paid	0.0	0.0
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs		0.0
Proceeds from long-term debt	0.0	0.0
Proceeds from revolving credit facility	0.0	0.0
Repayments of revolving credit facility	0.0	0.0
Repurchase of common shares	0.0	0.0
Repayments of bank overdrafts	0.0	0.0
Other financing activities	0.0	0.0
Intra-entity activity, net	(4.6)	(4.9)
Net cash used in financing activities	(4.6)	(4.9)
Cash and cash equivalents at beginning of period	0.1	0.1
Decrease in cash and cash equivalents	0.0	0.0
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Cash and cash equivalents at end of period	0.1	0.1
Term Loan
Financing activities
Proceeds from term and bridge loans	350.0	0.0
Repayments of debt	(365.7)	(12.0)
Term Loan | Consolidation, Eliminations
Financing activities
Proceeds from term and bridge loans	0.0
Repayments of debt	0.0	0.0
Term Loan | Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Proceeds from term and bridge loans	350.0
Repayments of debt	(365.7)	(12.0)
Term Loan | Non-Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Proceeds from term and bridge loans	0.0
Repayments of debt	0.0
Term Loan | Signet Jewelers Limited | Reportable Legal Entities
Financing activities
Proceeds from term and bridge loans	0.0
Repayments of debt	0.0	0.0
Term Loan | Signet UK Finance plc | Reportable Legal Entities
Financing activities
Proceeds from term and bridge loans	0.0
Repayments of debt	0.0	0.0
Securitization facility
Financing activities
Repayments of debt	(2,345.9)	(1,837.1)
Securitization facility | Consolidation, Eliminations
Financing activities
Repayments of debt	0.0	0.0
Securitization facility | Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Repayments of debt	0.0	0.0
Securitization facility | Non-Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Repayments of debt	(2,345.9)	(1,837.1)
Securitization facility | Signet Jewelers Limited | Reportable Legal Entities
Financing activities
Repayments of debt	0.0	0.0
Securitization facility | Signet UK Finance plc | Reportable Legal Entities
Financing activities
Repayments of debt	$ 0.0	$ 0.0