Recent Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Accounts receivable, less allowances	$ 372,531		$ 372,531		$ 362,479	$ 348,943
Inventories	258,374		258,374		233,054	241,962
Prepaid expenses and other current assets	53,281		53,281		47,105	32,526
Deferred income taxes	11,336		11,336		11,171	12,161
Liabilities
Accrued liabilities	203,481		203,481		194,777	181,241
Deferred income taxes	64,746		64,746		73,891	73,505
Stockholders' equity
Retained earnings	1,333,216		1,333,216		1,211,018	1,206,723
Accumulated other non-owner changes to equity	(152,132)	$ (117,202)	(152,132)	$ (117,202)		(106,399)	$ (200,828)
Consolidated Statement of Income
Net sales	369,797	357,156	1,111,772	1,063,451
Cost of sales	236,880	235,406	711,622	697,493
Operating profit	59,063	48,898	179,575	155,935
Income before income taxes	52,562	43,681	162,340	149,262
Income taxes	13,453	8,348	34,983	30,599
Net income	39,109	35,333	127,357	118,663
Other expense (income), net	2,447	1,469	5,157	(3,965)
Facility Closing [Member]
Consolidated Statement of Income
Curtailment gain				(7,217)
Settlement gain				(230)
Pensions [Member]
Consolidated Statement of Income
Curtailment gain	0	0	0	(7,217)
Settlement gain	0	298	0	(193)
Pensions [Member] | Facility Closing [Member]
Consolidated Statement of Income
Curtailment gain			(7,217)
Settlement gain			(230)	(230)
Accounting Standards Update 2017-07 [Member]
Consolidated Statement of Income
Other expense (income), net		$ 1,109		$ (4,739)
Accounting Standards Update 2018-02 [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
Stockholders' equity
Retained earnings	19,331		19,331
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Assets
Accounts receivable, less allowances	362,572		362,572			348,943
Inventories	266,843		266,843			241,962
Prepaid expenses and other current assets	39,241		39,241
Deferred income taxes	12,395		12,395			12,161
Liabilities
Accrued liabilities	193,363		193,363			181,241
Deferred income taxes	64,499		64,499			73,505
Stockholders' equity
Retained earnings	1,329,062		1,329,062			$ 1,206,723
Accumulated other non-owner changes to equity	(152,088)		(152,088)
Consolidated Statement of Income
Net sales	370,129		1,112,423
Cost of sales	236,601		712,069
Operating profit	59,674		179,779
Income before income taxes	53,173		162,544
Income taxes	13,619		35,046
Net income	39,554		127,498
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Assets
Accounts receivable, less allowances	9,959		9,959		13,536
Inventories	(8,469)		(8,469)		(8,908)
Prepaid expenses and other current assets	14,040		14,040		14,579
Deferred income taxes	(1,059)		(1,059)		(990)
Liabilities
Accrued liabilities	10,118		10,118		13,536
Deferred income taxes	247		247		386
Stockholders' equity
Retained earnings	4,154		4,154		$ 4,295
Accumulated other non-owner changes to equity	(44)		(44)
Consolidated Statement of Income
Net sales	(332)		(651)
Cost of sales	279		(447)
Operating profit	(611)		(204)
Income before income taxes	(611)		(204)
Income taxes	(166)		(63)
Net income	$ (445)		$ (141)