Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income	$ 158,350,000	$ 166,186,000	$ 59,415,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	99,059,000	94,238,000	90,150,000
Loss (gain) on disposition of property, plant and equipment	236,000	71,000	(246,000)
Stock compensation expense	13,306,000	12,158,000	12,279,000
Effect of U.S. Tax Reform on deferred tax assets	0	0	4,152,000
Non-cash impairment charge related to divestiture	5,600,000	0	0
Changes in assets and liabilities, net of the effects of acquisitions:
Accounts receivable	29,212,000	(10,960,000)	(50,082,000)
Inventories	11,482,000	(12,369,000)	(173,000)
Prepaid expenses and other current assets	(10,640,000)	(2,890,000)	(4,241,000)
Accounts payable	(22,546,000)	12,489,000	12,018,000
Accrued liabilities	2,336,000	(580,000)	14,439,000
Deferred income taxes	(12,025,000)	(18,876,000)	3,589,000
Long-term retirement benefits	(16,233,000)	1,632,000	(16,349,000)
Long-term tax liability	(6,949,000)	(6,809,000)	79,770,000
Other	(2,887,000)	2,909,000	(801,000)
Net cash provided by operating activities	248,301,000	237,199,000	203,920,000
Investing activities:
Proceeds from disposition of property, plant and equipment	577,000	1,374,000	2,594,000
Capital expenditures	(53,286,000)	(57,273,000)	(58,712,000)
Business acquisitions, net of cash acquired	(6,061,000)	(430,487,000)	(8,922,000)
Revenue Sharing Program payments	0	(5,800,000)	0
Other	(3,450,000)	(1,000,000)	(3,000,000)
Net cash used in investing activities	(62,220,000)	(493,186,000)	(68,040,000)
Financing activities:
Net change in other borrowings	5,490,000	(5,145,000)	(25,304,000)
Payments on long-term debt	(341,419,000)	(433,904,000)	(73,161,000)
Proceeds from the issuance of long-term debt	236,552,000	841,036,000	129,118,000
Proceeds from the issuance of common stock	5,492,000	1,131,000	2,408,000
Common stock repurchases	(50,347,000)	(138,275,000)	(40,791,000)
Dividends paid	(32,544,000)	(32,206,000)	(29,551,000)
Withholding taxes paid on stock issuances	(6,059,000)	(5,395,000)	(5,380,000)
Other	(9,158,000)	(11,678,000)	(21,090,000)
Net cash (used) provided by financing activities	(191,993,000)	215,564,000	(63,751,000)
Effect of exchange rate changes on cash flows	(1,002,000)	(4,148,000)	6,714,000
(Decrease) increase in cash and cash equivalents	(6,914,000)	(44,571,000)	78,843,000
Cash and cash equivalents at beginning of year	100,719,000	145,290,000	66,447,000
Cash and cash equivalents at end of year	$ 93,805,000	$ 100,719,000	$ 145,290,000