Benefit Plans - Pension Assets by Fair Value Level (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 186,336	$ 169,140
Approximate percentage of common stock invested in major industry	91.00%	90.00%
Approximate percentage of mutual funds actively managed	66.00%	68.00%
Approximate percentage of mutual funds indexed funds	34.00%	32.00%
Percentage of mutual funds' assets invested in U.S equities	5.00%	5.00%
Percent of mutual funds assets invested in non US equities	41.00%	38.00%
Percent of mutual funds assets invested in US fixed income securities	52.00%	54.00%
Percent of mutual funds assets invested in non US fixed income securities	2.00%	3.00%
Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 24,889	$ 28,418
Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	156,442	136,027
Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,005	4,695
Cash and Cash Equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,364	4,245
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,364	4,245
Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Cash and Cash Equivalents [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Common Stock [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	11,113	18,601
Common Stock [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	11,113	18,601
Common Stock [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Common Stock [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Mutual Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	164,854	141,599
Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	8,412	5,572
Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	156,442	136,027
Mutual Funds [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Limited Partnerships [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	5,005	4,695
Limited Partnerships [Member] | Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Limited Partnerships [Member] | Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	0	0
Limited Partnerships [Member] | Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 5,005	$ 4,695