EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ 63,716	[1]	$ 72,461	[2]	$ 85,452	[3]	$ 71,480	[4]	$ 86,839	[1]	$ 70,539	[2]	$ 68,864	[3]	$ 60,824	[4]	$ 293,109	$ 287,066	$ 247,503
Denominator:
Basic weighted average shares outstanding (in shares)																	61,960,000	64,886,000	65,739,000
Effect of dilutive securities - stock options and awards (in shares)																	698,000	796,000	904,000
Diluted weighted average shares outstanding (in shares)																	62,658,000	65,682,000	66,643,000
Basic earnings per share (in dollars per share)	$ 1.04	[5]	$ 1.18	[5]	$ 1.37	[5]	$ 1.13	[5]	$ 1.36	[5]	$ 1.09	[5]	$ 1.05	[5]	$ 0.93	[5]	$ 4.73	$ 4.42	$ 3.76
Diluted earnings per share (in dollars per share)	$ 1.03	[5]	$ 1.17	[5]	$ 1.36	[5]	$ 1.12	[5]	$ 1.35	[5]	$ 1.07	[5]	$ 1.04	[5]	$ 0.92	[5]	$ 4.68	$ 4.37	$ 3.71
Anti-dilutive shares excluded from the computation of diluted earnings per share																	524,110	324,688	157,033

[1] 2019 includes special item charges of $8,851 ($7,284 after-tax) for Rationalization and asset impairment charges. 2018 includes special item charges of $1,696 ($1,272 after-tax) for pension settlement charges, $932 ($841 gain after-tax) for Rationalization and asset impairment charges and gains or losses on the disposal of assets, a $4,424 credit related to the U.S. Tax Act and acquisition-related items including $833 ($690 after-tax) for acquisition transaction and integration costs.

[2] 2019 includes special item charges of $1,495 ($1,240 after-tax) for Rationalization and asset impairment charges, $1,609 for amortization of step up in value of acquired inventories and $7,601 for a gain on change in control related to the acquisition of Askaynak. 2018 includes special item charges of $4,232 ($3,176 after-tax) for pension settlement charges, $2,636 ($2,575 after-tax) for Rationalization and asset impairment charges, an adjustment to taxes on unremitted foreign earnings related to the U.S. Tax Act of $2,323 and acquisition-related items including $970 ($797 after-tax) for acquisition transaction and integration costs.

[3] 2019 includes special item charges of $3,554 ($2,586 after-tax) for gains on the disposal of assets, $1,399 ($1,049 after-tax) for amortization of step up in value of acquired inventories, $1,014 ($867 after-tax) for acquisition transaction and integration costs, $1,307 ($937 after-tax) for Rationalization and asset impairment charges and $4,852 for the settlement of a tax item as well as tax deductions associated with an investment in a subsidiary. 2018 includes special item charges of $11,542 ($10,362 after-tax) for Rationalization and asset impairment charges and $788 ($675 after-tax) for acquisition transaction and integration costs.

[4] 2019 includes special item charges of $3,535 ($2,814 after-tax) for Rationalization and asset impairment charges and $790 ($698 after-tax) for acquisition transaction and integration costs. 2018 includes special item charges of $758 ($569 after-tax) for pension settlement charges, $10,175 ($7,870 after-tax) for Rationalization and asset impairment charges, an adjustment to taxes on unremitted foreign earnings related to the U.S. Tax Act of $2,500 and $1,907 ($1,520 after-tax) for acquisition transaction and integration costs.

[5] The quarterly earnings per share ("EPS") amounts are each calculated independently. Therefore, the sum of the quarterly EPS amounts may not equal the annual totals.