Pension, Profit Sharing & Other Post-Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension, profit sharing and other post-retirement health benefit expense charged to operations	$ 2.6	$ 2.4	$ 8.5	$ 7.9
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Estimated total employer contributions in current fiscal year			6.0
Contributions by employer in current year			$ 4.7
Estimated future employer contributions in fiscal year 2015					$ 7.9