Capital Transactions - Summary of the Awards Each Year (Detail) - Class B Common Stock [Member] - shares	9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017
Schedule of Capitalization, Equity [Line Items]
Date of approval for award	Mar. 06, 2018	Mar. 07, 2017
Fiscal year of service covered by award	2017	2016
Shares settled in cash to satisfy tax withholding obligations	16,504	18,980
Increase in Class B Common Stock shares outstanding	20,296	21,020
Total Class B Common Stock awarded	36,800	40,000