Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Fair value of long-term debt

Carrying amounts and the related estimated fair values of the Company’s long-term debt financial instruments not measured at fair value on a recurring basis at December 31, 2017 and December 25, 2016 are presented in the following table:

	As of December 31, 2017						As of December 25, 2016
$ in millions	Principal		Carrying Amount		Fair Value		Principal		Carrying Amount		Fair Value
Long-term debt	$	300.8	$	294.3	$	312.7	$	437.3	$	432.0	$	423.6