Benefit Plans - Liability Under Executive Benefit Plans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Jan. 01, 2017
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	$ 27,024	$ 23,858
Supplemental Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	8,205	7,339
Noncurrent liabilities	74,958	70,709
Total liability	83,163	78,048
Long-Term Retention Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	3	2
Noncurrent liabilities	2,563	1,256
Total liability	2,566	1,258
Retention Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	2,949	3,359
Noncurrent liabilities	42,694	44,480
Total liability	45,643	47,839
Performance Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	5,561	5,282
Noncurrent liabilities	4,527	5,651
Total liability	$ 10,088	$ 10,933