Retirement Plans - Target allocation ranges (Details) - Pension Benefits	Dec. 29, 2018
Real Estate Non-U.S.
Target allocation ranges
Target plan asset allocations	13.00%
Minimum | Equity securities, U.S.
Target allocation ranges
Target plan asset allocations	17.00%
Minimum | Equity securities, Non-U.S.
Target allocation ranges
Target plan asset allocations	51.00%
Minimum | International Equity Securities
Target allocation ranges
Target plan asset allocations	8.00%
Minimum | Global equities
Target allocation ranges
Target plan asset allocations	5.00%
Minimum | Debt security U.S.
Target allocation ranges
Target plan asset allocations	27.00%
Minimum | Debt security Non-U.S.
Target allocation ranges
Target plan asset allocations	26.00%
Minimum | Real Estate U.S.
Target allocation ranges
Target plan asset allocations	7.00%
Minimum | Real Estate Non-U.S.
Target allocation ranges
Target plan asset allocations	0.00%
Minimum | Private investment partnerships
Target allocation ranges
Target plan asset allocations	5.00%
Minimum | Hedge funds
Target allocation ranges
Target plan asset allocations	0.00%
Maximum | Equity securities, U.S.
Target allocation ranges
Target plan asset allocations	33.00%
Maximum | Equity securities, Non-U.S.
Target allocation ranges
Target plan asset allocations	74.00%
Maximum | International Equity Securities
Target allocation ranges
Target plan asset allocations	19.00%
Maximum | Global equities
Target allocation ranges
Target plan asset allocations	17.00%
Maximum | Debt security U.S.
Target allocation ranges
Target plan asset allocations	38.00%
Maximum | Debt security Non-U.S.
Target allocation ranges
Target plan asset allocations	46.00%
Maximum | Real Estate U.S.
Target allocation ranges
Target plan asset allocations	13.00%
Maximum | Private investment partnerships
Target allocation ranges
Target plan asset allocations	11.00%
Maximum | Hedge funds
Target allocation ranges
Target plan asset allocations	0.00%