INCOME TAXES - Effective tax rate - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective income tax rate differs from the statutory rate
U.S. statutory rate (as a percent)	21.00%	35.00%	35.00%
State income taxes, net (as a percent)	0.50%	1.60%	1.00%
Exempt municipal bond interest (as a percent)	(0.10%)	(0.10%)	(0.10%)
Foreign tax rates (as a percent)	2.10%	0.50%	(0.40%)
Qualified domestic production activities deduction (as a percent)		(0.80%)	(2.70%)
Tax credits receivable (as a percent)		(1.40%)	(0.50%)
Adjustment of deferred tax balances (as a percent)	0.10%	(24.20%)	(0.50%)
Reserve for uncertain tax benefits (as a percent)	(1.00%)	(0.30%)
Worthless stock deduction (as a percent)		(3.80%)
Other, net (as a percent)	(0.20%)	(1.90%)	(0.60%)
Effective income tax rate (as a percent)	22.40%	4.60%	31.20%
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2026	$ 288
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2027	61
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2028	183
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2029	104
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2030	316
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2031	421
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2032	317
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2033	128
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2034	443
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2035	560
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2036	830
Tax benefit due to 2017 Tax Cuts and Jobs Act		$ (20,318)
Portion of unrecognized tax benefits that, if recognized, would favorably affect annual effective income tax rate	1,765	2,475
Interest and penalties included in liability for uncertain tax positions	477	475
Reconciliation of the beginning and ending balances of the total amounts of unrecognized tax benefits
Unrecognized tax benefits at the beginning of the period	4,342	4,746	$ 4,680
Increases in tax positions for the current year	448	394	803
Reductions in tax positions for lapse of statute of limitations	(751)	(793)	(718)
Reductions in tax positions relating to settlements with taxing authorities			(27)
Increases in prior period unrecognized tax benefits			8
Decreases in prior period unrecognized tax benefits	(700)	(5)
Unrecognized tax benefits at the end of the period	3,339	$ 4,342	$ 4,746
Canada
Effective income tax rate differs from the statutory rate
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2029	1,232
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2031	612
Mexico
Effective income tax rate differs from the statutory rate
Tax benefits of foreign subsidiary tax loss carry forwards expiring in 2036	$ 236