Condensed consolidating financial information - Condensed consolidated statement of cash flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jul. 29, 2017	Jul. 30, 2016
Cash flows from operating activities
Net cash provided by (used in) operating activities	$ 409.8	$ 309.2
Investing activities
Purchase of property, plant and equipment	(105.7)	(101.0)
Investment in subsidiaries		0.0
Purchase of available-for-sale securities	(1.3)	(2.6)
Proceeds from available-for-sale securities	0.6	3.1
Net cash used in investing activities	(106.4)	(100.5)
Financing activities
Dividends paid on common shares	(39.0)	(37.9)
Dividends paid on redeemable convertible preferred shares	(19.1)	0.0
Intra-entity dividends paid	0.0	0.0
Proceeds from issuance of common shares	0.2	0.4
Excess tax benefit from exercise of share awards	0.0	1.3
Proceeds from long-term debt	1,242.9	1,278.9
Proceeds from revolving credit facility	550.0	318.0
Repayments of revolving credit facility	(303.0)	(118.0)
Payment of debt issuance costs	0.0	(2.7)
Repurchase of common shares	(460.0)	(375.0)
Net settlement of equity based awards	(3.2)	(4.8)
Capital lease payments	0.0	(0.1)
Proceeds from short-term borrowings	(3.1)	(2.3)
Intra-entity activity, net	0.0	0.0
Net cash used in financing activities	(286.2)	(228.6)
Cash and cash equivalents at beginning of period	98.7	137.7
Decrease in cash and cash equivalents	17.2	(19.9)
Effect of exchange rate changes on cash and cash equivalents	3.2	0.9
Cash and cash equivalents at end of period	119.1	118.7
Consolidation, Eliminations
Cash flows from operating activities
Net cash provided by (used in) operating activities	(1,118.0)	(941.0)
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
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	941.0
Proceeds from issuance of common shares	0.0	(91.0)
Excess tax benefit from exercise of share awards		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
Payment of debt issuance costs		0.0
Repurchase of common shares	0.0	0.0
Net settlement of equity based awards	0.0	0.0
Capital lease payments		0.0
Proceeds from short-term borrowings	0.0
Intra-entity activity, net	0.0	0.0
Net cash used in financing activities	1,118.0	850.0
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
Signet Jewelers Limited | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	617.7	549.7
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
Net cash used in investing activities	0.0	(91.0)
Financing activities
Dividends paid on common shares	(39.0)	(37.9)
Dividends paid on redeemable convertible preferred shares	(19.1)
Intra-entity dividends paid	0.0	0.0
Proceeds from issuance of common shares	0.2	0.4
Excess tax benefit from exercise of share awards		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
Payment of debt issuance costs		0.0
Repurchase of common shares	(460.0)	(375.0)
Net settlement of equity based awards	(3.2)	(4.8)
Capital lease payments		0.0
Proceeds from short-term borrowings	0.0
Intra-entity activity, net	(97.6)	(43.1)
Net cash used in financing activities	(618.7)	(460.4)
Cash and cash equivalents at beginning of period	1.7	1.9
Decrease in cash and cash equivalents	(1.0)	(1.7)
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Cash and cash equivalents at end of period	0.7	0.2
Signet UK Finance plc | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	0.1	0.2
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
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 common shares	0.0	0.0
Excess tax benefit from exercise of share awards		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
Payment of debt issuance costs		0.0
Repurchase of common shares	0.0	0.0
Net settlement of equity based awards	0.0	0.0
Capital lease payments		0.0
Proceeds from short-term borrowings	0.0	0.0
Intra-entity activity, net	(0.1)	(0.2)
Net cash used in financing activities	(0.1)	(0.2)
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
Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	479.3	383.3
Investing activities
Purchase of property, plant and equipment	(105.6)	(101.0)
Purchase of available-for-sale securities	0.0	0.0
Proceeds from available-for-sale securities	0.0	0.0
Net cash used in investing activities	(105.6)	(101.0)
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	(800.0)	(650.0)
Proceeds from issuance of common shares	0.0	91.0
Excess tax benefit from exercise of share awards		1.3
Proceeds from long-term debt	0.0	0.0
Proceeds from revolving credit facility	550.0	318.0
Repayments of revolving credit facility	(303.0)	(118.0)
Payment of debt issuance costs		(2.1)
Repurchase of common shares	0.0	0.0
Net settlement of equity based awards	0.0	0.0
Capital lease payments		(0.1)
Proceeds from short-term borrowings	(3.1)	(2.3)
Intra-entity activity, net	208.1	68.0
Net cash used in financing activities	(357.0)	(301.7)
Cash and cash equivalents at beginning of period	70.3	102.0
Decrease in cash and cash equivalents	16.7	(19.4)
Effect of exchange rate changes on cash and cash equivalents	3.2	1.2
Cash and cash equivalents at end of period	90.2	83.8
Non-Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by (used in) operating activities	430.7	317.0
Investing activities
Purchase of property, plant and equipment	(0.1)
Purchase of available-for-sale securities	(1.3)	(2.6)
Proceeds from available-for-sale securities	0.6	3.1
Net cash used in investing activities	(0.8)	0.5
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)	(291.0)
Proceeds from long-term debt	1,242.9	1,278.9
Proceeds from revolving credit facility	0.0	0.0
Repayments of revolving credit facility	0.0	0.0
Payment of debt issuance costs		(0.6)
Repurchase of common shares	0.0	0.0
Net settlement of equity based awards	0.0	0.0
Capital lease payments		0.0
Proceeds from short-term borrowings	0.0
Intra-entity activity, net	(110.4)	(24.7)
Net cash used in financing activities	(428.4)	(316.3)
Cash and cash equivalents at beginning of period	26.6	33.7
Decrease in cash and cash equivalents	1.5	1.2
Effect of exchange rate changes on cash and cash equivalents		(0.3)
Cash and cash equivalents at end of period	28.1	34.6
Term Loan
Financing activities
Repayments of long-term debt	(9.0)	(7.5)
Term Loan | Consolidation, Eliminations
Financing activities
Repayments of long-term debt	0.0	0.0
Term Loan | Signet Jewelers Limited | Reportable Legal Entities
Financing activities
Repayments of long-term debt	0.0	0.0
Term Loan | Signet UK Finance plc | Reportable Legal Entities
Financing activities
Repayments of long-term debt	0.0	0.0
Term Loan | Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Repayments of long-term debt	(9.0)	(7.5)
Term Loan | Non-Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Repayments of long-term debt	0.0
Securitization facility
Financing activities
Repayments of long-term debt	(1,242.9)	(1,278.9)
Securitization facility | Consolidation, Eliminations
Financing activities
Repayments of long-term debt	0.0	0.0
Securitization facility | Signet Jewelers Limited | Reportable Legal Entities
Financing activities
Repayments of long-term debt	0.0	0.0
Securitization facility | Signet UK Finance plc | Reportable Legal Entities
Financing activities
Repayments of long-term debt	0.0	0.0
Securitization facility | Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Repayments of long-term debt	0.0	0.0
Securitization facility | Non-Guarantor Subsidiaries | Reportable Legal Entities
Financing activities
Repayments of long-term debt	$ (1,242.9)	$ (1,278.9)