Employee Benefit Plans (Plan Assets) (Details) (USD $)	12 Months Ended
	Dec. 27, 2014	Dec. 28, 2013	Dec. 29, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 6,411,000
Common Stock [Member]
Target Allocations
Target Allocation, Total	49.70%
Debt Securities [Member]
Target Allocations
Target Allocation, Total	31.20%
Other Plan Asset Categories [Member]
Target Allocations
Target Allocation, Total	19.10%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer	6,874,000	9,570,000
Target Allocations
Fair value of plan assets	281,290,000	272,659,000	238,672,000
Pension Benefits [Member] | Cash [Member]
Target Allocations
Fair value of plan assets	1,000	1,004,000
Pension Benefits [Member] | Common Stock [Member]
Target Allocations
Fair value of plan assets	85,818,000	102,916,000
Pension Benefits [Member] | Debt Securities [Member]
Target Allocations
Fair value of plan assets	72,948,000	66,204,000
Pension Benefits [Member] | Mutual Funds [Member]
Target Allocations
Fair value of plan assets	120,409,000	100,762,000
Pension Benefits [Member] | Other Plan Asset Categories [Member]
Target Allocations
Fair value of plan assets	2,114,000	1,773,000
Pension Benefits [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member]
Target Allocations
Fair value of plan assets	217,785,000	227,029,000
Pension Benefits [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Cash [Member]
Target Allocations
Fair value of plan assets	1,000	1,004,000
Pension Benefits [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Common Stock [Member]
Target Allocations
Fair value of plan assets	80,692,000	97,857,000
Pension Benefits [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Debt Securities [Member]
Target Allocations
Fair value of plan assets	69,716,000	62,717,000
Pension Benefits [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Mutual Funds [Member]
Target Allocations
Fair value of plan assets	67,079,000	65,152,000
Pension Benefits [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Other Plan Asset Categories [Member]
Target Allocations
Fair value of plan assets	297,000	299,000
Pension Benefits [Member] | Significant Other Observable Inputs Level 2 [Member]
Target Allocations
Fair value of plan assets	61,734,000	44,204,000
Pension Benefits [Member] | Significant Other Observable Inputs Level 2 [Member] | Cash [Member]
Target Allocations
Fair value of plan assets	0	0
Pension Benefits [Member] | Significant Other Observable Inputs Level 2 [Member] | Common Stock [Member]
Target Allocations
Fair value of plan assets	5,126,000	5,059,000
Pension Benefits [Member] | Significant Other Observable Inputs Level 2 [Member] | Debt Securities [Member]
Target Allocations
Fair value of plan assets	3,232,000	3,487,000
Pension Benefits [Member] | Significant Other Observable Inputs Level 2 [Member] | Mutual Funds [Member]
Target Allocations
Fair value of plan assets	53,330,000	35,610,000
Pension Benefits [Member] | Significant Other Observable Inputs Level 2 [Member] | Other Plan Asset Categories [Member]
Target Allocations
Fair value of plan assets	46,000	48,000
Pension Benefits [Member] | Significant Unobservable Inputs Level 3 [Member]
Target Allocations
Fair value of plan assets	1,771,000	1,426,000
Pension Benefits [Member] | Significant Unobservable Inputs Level 3 [Member] | Cash [Member]
Target Allocations
Fair value of plan assets	0	0
Pension Benefits [Member] | Significant Unobservable Inputs Level 3 [Member] | Common Stock [Member]
Target Allocations
Fair value of plan assets	0	0
Pension Benefits [Member] | Significant Unobservable Inputs Level 3 [Member] | Debt Securities [Member]
Target Allocations
Fair value of plan assets	0	0
Pension Benefits [Member] | Significant Unobservable Inputs Level 3 [Member] | Mutual Funds [Member]
Target Allocations
Fair value of plan assets	0	0
Pension Benefits [Member] | Significant Unobservable Inputs Level 3 [Member] | Other Plan Asset Categories [Member]
Target Allocations
Fair value of plan assets	$ 1,771,000	$ 1,426,000