Reconciliation of Average Number of Common Shares Outstanding to Average Number of Diluted Shares Outstanding (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Average number of common shares outstanding	41,957,000	42,039,000	41,924,000	42,223,000
Incremental shares from assumed exercises of stock options	71,000	131,000	89,000	118,000
Average number of common shares and common share equivalents outstanding	42,028,000	42,170,000	42,013,000	42,341,000