Pension and Other Retirement Plans - Defined Benefit Pension Plans and Other Post Retirement Plans Summarized Info (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 28, 2014
Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligations, beginning of year	$ 1,986,971	$ 2,124,373
Service cost	692	709	$ 463
Interest cost	82,724	81,815	82,109
Plan amendments	1,025	0
Impact of Medicare Reform Act	0	0
Actuarial loss (gain)	22,615	(114,431)
Benefits paid	(103,764)	(105,495)
Projected benefit obligations, end of year	1,990,263	1,986,971	2,124,373
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plans’ assets, beginning of year	1,530,898	1,655,257
Actual return on plans’ assets	118,728	(19,113)
Employer contributions	0	249
Benefits paid	(103,764)	(105,495)
Fair value of plans’ assets, end of year	1,545,862	1,530,898	1,655,257
Under funded status of the plans	(444,401)	(456,073)
Other Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligations, beginning of year	10,055	14,005
Service cost	0	81	328
Interest cost	320	451	1,466
Plan amendments	0	(3,887)
Impact of Medicare Reform Act	60	72
Actuarial loss (gain)	(496)	726
Benefits paid	(1,064)	(1,393)
Projected benefit obligations, end of year	8,875	10,055	14,005
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plans’ assets, beginning of year	0	0
Actual return on plans’ assets	0	0
Employer contributions	1,064	1,393
Benefits paid	(1,064)	(1,393)
Fair value of plans’ assets, end of year	0	0	$ 0
Under funded status of the plans	$ (8,875)	$ (10,055)