Pension Benefits - Reconciliation of Significant Observable Inputs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2015	Dec. 28, 2014
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Actual gain on plan assets still held and sold during the period	$ (2,221)	$ (806)
Capital contribution	1,288	2,008
Return of Capital	(5,138)	(5,043)
Level 3 [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at beginning of year	67,021	70,862
Balance at end of year	60,950	67,021
Hedge Fund [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Actual gain on plan assets still held and sold during the period	(51)
Capital contribution	0
Return of Capital	0
Hedge Fund [Member] | Level 3 [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at beginning of year	31,294
Balance at end of year	31,243	31,294
Private Equity [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Actual gain on plan assets still held and sold during the period	(2,170)	(1,775)
Capital contribution	1,288	2,008
Return of Capital	(5,138)	(5,043)
Private Equity [Member] | Level 3 [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at beginning of year	35,727	40,537
Balance at end of year	29,707	35,727
Real Estate Funds [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Actual gain on plan assets still held and sold during the period		969
Capital contribution		0
Return of Capital		0
Real Estate Funds [Member] | Level 3 [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at beginning of year	$ 31,294	30,325
Balance at end of year		$ 31,294