Supplemental Stockholders' Equity Information - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	$ 1,042,641	$ 897,363
Income tax expense/(benefit)	1,399	2,820
Other comprehensive income, net of tax	3,922	7,842
Balance, end of period	1,059,814	958,077
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	4,677
Other comprehensive (loss)/income before reclassifications, before tax	(1,649)
Amounts reclassified from accumulated other comprehensive loss, before tax	0
Income tax expense/(benefit)	(431)
Other comprehensive income, net of tax	(1,218)
Balance, end of period	3,459
Funded Status of Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(520,308)
Other comprehensive (loss)/income before reclassifications, before tax	0
Amounts reclassified from accumulated other comprehensive loss, before tax	4,896
Income tax expense/(benefit)	1,288
Other comprehensive income, net of tax	3,608
Balance, end of period	(516,700)
Net unrealized Loss on available-for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(2,093)
Other comprehensive (loss)/income before reclassifications, before tax	2,074
Amounts reclassified from accumulated other comprehensive loss, before tax	0
Income tax expense/(benefit)	542
Other comprehensive income, net of tax	1,532
Balance, end of period	(561)
Parent
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	1,040,781	897,279
Other comprehensive (loss)/income before reclassifications, before tax	425
Amounts reclassified from accumulated other comprehensive loss, before tax	4,896
Income tax expense/(benefit)	1,399
Other comprehensive income, net of tax	3,922	7,842
Balance, end of period	1,057,954	957,991
Accumulated Other Comprehensive Loss, Net of Income Taxes
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(517,724)	(423,029)
Other comprehensive income, net of tax	3,922	7,842
Balance, end of period	$ (513,802)	$ (509,322)