Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 28, 2018 USD ($) $ / shares shares	[1]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding, Options Balance | shares	680,000
Number of shares outstanding, Options Granted | shares	98,000
Number of shares outstanding, Options forfeited and expired | shares	0
Number of shares outstanding, Options Exercised | shares	0
Number of shares outstanding, Options Balance | shares	778,000
Number of shares outstanding, Exercisable | shares	512,000
Weighted-average exercise price, Options Balance | $ / shares	$ 18.39
Weighted-average exercise price, Options Granted | $ / shares	37.45
Weighted-average exercise price, Options forfeited and expired | $ / shares	0
Weighted-average exercise price, Options Exercised | $ / shares	0
Weighted-average exercise price, Options Balance | $ / shares	20.80
Weighted-average exercise price, Exercisable | $ / shares	$ 15.76
Weighted average remaining contractual term, Balance	5 years 8 months 23 days
Weighted average remaining contractual term, Exercisable	4 years 5 months 19 days
Aggregate intrinsic value, Balance | $	$ 22,659
Aggregate intrinsic value, Exercisable | $	$ 17,488

[1] Does not include restricted stock or employee stock purchase plans.