CONSOLIDATED QUARTERLY FINANCIAL DATA (UNAUDITED) - Summary of the Unaudited Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Net sales	$ 610,196	$ 553,073	$ 612,690	$ 491,319	$ 543,444	$ 425,098	$ 435,903	$ 362,716	$ 462,057	$ 464,272	$ 471,439	$ 447,676	$ 2,267,278	$ 1,767,161	$ 1,845,444
Gross profit	69,056	65,162	85,315	64,119	72,876	60,963	67,679	59,357	71,485	83,459	91,064	79,526	283,651	260,875	325,534
Net income for the year	$ 11,584	$ 4,664	$ 31,902	$ 21,272	$ 49,357	$ 18,947	$ 22,945	$ 20,173	$ 23,000	$ 33,378	$ 35,532	$ 27,523	$ 69,421	$ 111,422	$ 119,433
Basic net income per share (in dollars per share)	$ 0.21	$ 0.08	$ 0.55	$ 0.37	$ 0.84	$ 0.32	$ 0.38	$ 0.34	$ 0.37	$ 0.52	$ 0.55	$ 0.42	$ 1.22	$ 1.88	$ 1.87
Diluted net income per share (in usd per share)	$ 0.21	$ 0.08	$ 0.54	$ 0.35	$ 0.80	$ 0.30	$ 0.36	$ 0.32	$ 0.36	$ 0.51	$ 0.53	$ 0.42	$ 1.19	$ 1.78	$ 1.82