Derivative financial instruments - Fair Values of Derivative Instruments (Details) - USD ($) $ in Millions	Jul. 03, 2021	Jan. 02, 2021
Derivatives, Fair Value
Net	$ (77.1)	$ (103.2)
Prepaid expenses and other assets
Derivatives, Fair Value
Derivative assets	1.5	1.7
Other non- current assets
Derivatives, Fair Value
Derivative assets	1.3	0.0
Accrued expenses and other current liabilities
Derivatives, Fair Value
Derivative liabilities	(46.4)	(16.7)
Other non- current liabilities
Derivatives, Fair Value
Derivative liabilities	(33.5)	(88.2)
Derivatives designated as hedging instruments: | —Currency swaps
Derivatives, Fair Value
Net	(31.5)	(41.5)
Derivatives designated as hedging instruments: | —Currency swaps | Prepaid expenses and other assets
Derivatives, Fair Value
Derivative assets	0.0	1.1
Derivatives designated as hedging instruments: | —Currency swaps | Accrued expenses and other current liabilities
Derivatives, Fair Value
Derivative liabilities	(31.5)
Derivatives designated as hedging instruments: | —Currency swaps | Other non- current liabilities
Derivatives, Fair Value
Derivative liabilities	0.0	(42.6)
Derivatives designated as hedging instruments: | —Interest rate caps
Derivatives, Fair Value
Net	(2.6)	(3.4)
Derivatives designated as hedging instruments: | —Interest rate caps | Accrued expenses and other current liabilities
Derivatives, Fair Value
Derivative liabilities	(1.3)	(1.4)
Derivatives designated as hedging instruments: | —Interest rate caps | Other non- current liabilities
Derivatives, Fair Value
Derivative liabilities	(1.3)	(2.0)
Derivatives designated as hedging instruments: | —Interest rate swaps
Derivatives, Fair Value
Net	(44.3)	(57.0)
Derivatives designated as hedging instruments: | —Interest rate swaps | Other non- current assets
Derivatives, Fair Value
Derivative assets	1.3
Derivatives designated as hedging instruments: | —Interest rate swaps | Accrued expenses and other current liabilities
Derivatives, Fair Value
Derivative liabilities	(13.4)	(13.4)
Derivatives designated as hedging instruments: | —Interest rate swaps | Other non- current liabilities
Derivatives, Fair Value
Derivative liabilities	(32.2)	(43.6)
Derivatives not designated as hedging instruments: | —Currency forward contracts
Derivatives, Fair Value
Net	1.3	(1.3)
Derivatives not designated as hedging instruments: | —Currency forward contracts | Prepaid expenses and other assets
Derivatives, Fair Value
Derivative assets	1.5	0.6
Derivatives not designated as hedging instruments: | —Currency forward contracts | Accrued expenses and other current liabilities
Derivatives, Fair Value
Derivative liabilities	$ (0.2)	$ (1.9)