NET INCOME PER COMMON SHARE - Income Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended			6 Months Ended
	Jul. 01, 2018	Jun. 25, 2017		Jul. 01, 2018	Jun. 25, 2017
Earnings Per Share [Abstract]
Net income for basic and diluted per share calculation	$ 34,860	$ 21,260		$ 64,928	$ 38,727
Weighted average shares outstanding - basic (in shares)	24,202	24,600	[1]	24,472	23,759	[1]
Effect of potentially dilutive securities (in shares)	313	390		340	426
Weighted average common shares outstanding - diluted (in shares)	24,515	24,990	[1]	24,812	24,185	[1]
Basic net income per common share (in dollars per share)	$ 1.44	$ 0.86	[1]	$ 2.65	$ 1.63	[1]
Diluted net income per common share (in dollars per share)	$ 1.42	$ 0.85	[1]	$ 2.62	$ 1.60	[1]

[1] Net income per common share and weighted average shares outstanding, on both a basic and diluted basis, for the second quarter and six months ended June 25, 2017, have been retroactively adjusted to reflect the impact of the three-for-two stock split paid on December 8, 2017.