NET INCOME PER COMMON SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended								12 Months Ended
	Feb. 25, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income		$ 19,984	$ 21,317	$ 27,416	$ 20,849	$ 26,970	$ 27,934	$ 34,860	$ 30,068	$ 89,566	$ 119,832	$ 85,718
Weighted average shares outstanding - basic (in shares)										23,058	23,995	24,230
Effect of potentially dilutive securities (in shares)										222	322	413
Weighted average common shares outstanding - diluted (in shares)										23,280	24,317	24,643
Basic net income per common share (in USD per share)		$ 0.87	$ 0.92	$ 1.19	$ 0.90	$ 1.17	$ 1.17	$ 1.44	$ 1.22	$ 3.88	$ 4.99	$ 3.54
Diluted net income per common share (in USD per share)		0.86	0.92	1.18	0.90	$ 1.15	$ 1.15	$ 1.42	$ 1.20	3.85	4.93	3.48
Cash dividends paid per common share (in USD per share)		$ 0.25	$ 0	$ 0	$ 0					$ 0.25	$ 0	$ 0
Subsequent Event
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Cash dividends paid per common share (in USD per share)	$ 0.25