Quarterly report pursuant to Section 13 or 15(d)

Pension Plans - Components of Pension Cost (Details)

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Pension Plans - Components of Pension Cost (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jul. 01, 2017
Jul. 02, 2016
Jul. 01, 2017
Jul. 02, 2016
Compensation and Retirement Disclosure [Abstract]        
Service cost – benefits earned during the period $ 6,115 $ 6,507 $ 12,531 $ 12,956
Interest cost on projected benefit obligations 14,709 17,041 29,524 34,075
Expected return on plan assets (23,797) (24,926) (47,152) (49,845)
Amortization of deferred amounts:        
Net deferred actuarial losses 10,002 16,319 21,384 32,625
Deferred prior service costs 645 645 1,357 1,292
Net periodic pension cost $ 7,674 $ 15,586 $ 17,644 $ 31,103