Reconciliation of Average Number of Common Shares and Common Share Equivalents Outstanding (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Average number of common shares outstanding	41,101,000	41,957,000	41,530,000	41,924,000
Incremental shares from assumed exercises of stock options	36,000	71,000	46,000	89,000
Average number of common shares and common share equivalents outstanding	41,137,000	42,028,000	41,576,000	42,013,000