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Share Plans (Schedule of Share Option Activity) (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 27, 2019
Dec. 28, 2018
Dec. 29, 2017
Dec. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value $ 9.66 $ 5.32 $ 18.36  
Intrinsic value of options vested $ 0.3 $ 0.2 $ 1.4  
Share Option Activity [Roll Forward]        
Beginning balance 7,007,051 4,643,984 3,386,694  
Granted 1,378,175 3,159,521 1,719,532  
Exercised (45,324) (39,949) (113,605)  
Expired/Forfeited (1,449,202) (756,505) (348,637)  
Ending balance 6,890,700 7,007,051 4,643,984  
Share options vested and unvested expected to vest 6,376,302      
Share options exerciseable 3,349,227      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]        
Weighted-average exercise price, outstanding share options $ 36.39 $ 38.74 $ 57.78 $ 61.24
Weighted-average exercise price, granted share options 22.09 13.92 51.57  
Weighted-average exercise price, exercised share options 20.67 32.00 47.74  
Weighted-average exercise price, expired and forfeited share options 34.80 $ 52.63 $ 68.08  
Weighted-average exercise price, vested and unvested expected to vest share options 37.58      
Weighted-average exercise price, exercisable share options $ 49.80      
Weighted-average remaining contractual term, outstanding share options 1 year 7 months 6 days      
Weighted-average remaining contractual term, vested and unvested expected to vest share options 7 years 1 month 6 days      
Weighted-average remaining contractual term, exercisable share options 1 year 2 months 12 days      
Aggregate intrinsic value, outstanding share options $ 0.0      
Aggregate intrinsic value, vested and unvested expected to vest share options 0.0      
Aggregate intrinsic value, exercisable share options 0.0      
Tax benefit from stock options exercised $ 0.1 $ 0.1 $ 0.5