Benefit Plans - Change in Plan Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Jan. 01, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 227,549
Fair value of plan assets at end of year	257,790	$ 227,549
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	228,256	214,055
Actual return on plan assets	29,766	12,313
Employer contributions	11,600	11,120
Benefits paid	(11,109)	(9,232)
Fair value of plan assets at end of year	$ 258,513	$ 228,256