Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 63,039	$ 52,706	$ 58,297
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	12,557	12,395	12,306
Amortization	7,009	6,811	4,325
Equity in undistributed earnings of associated companies, net of dividends	(1,969)	578	(3,180)
Deferred income taxes	5,488	(2,401)	1,007
Uncertain tax positions (non-deferred portion)	(3,206)	(1,122)	(1,256)
Deferred compensation and other, net	(424)	14	3,174
Stock-based compensation	6,349	5,919	5,309
Restructuring and related activities	(439)	6,790	0
(Gain) loss on disposal of property, plant and equipment and other assets	(18)	(12)	(86)
Insurance settlement realized	(1,023)	(760)	(1,907)
Pension and other postretirement benefits contributions	(3,420)
Pension And Other Postretirement Benefit Expense		2,591	1,265
(Decrease) increase in cash from changes in current assets and current liabilities, net of acquisitions:
Accounts receivable	(11,705)	(188)	(24,944)
Inventories	(1,870)	1,292	(5,484)
Prepaid expenses and other current assets	(703)	(721)	2,003
Accounts payable and accrued liabilities	14,566	(9,040)	2,999
Change in restructuring liabilities	(5,252)	(490)	0
Estimated taxes on income	(5,226)	(930)	862
Net cash provided by operating activities	73,753	73,432	54,690
Cash flows from investing activities
Investments in property, plant and equipment	(9,954)	(11,033)	(13,052)
Payments related to acquisitions, net of cash acquired	(15,024)	(24,058)	(73,527)
Proceeds from disposition of assets	186	135	201
Insurance settlement interest earned	32	35	44
Change in restricted cash, net	991	725	1,863
Net cash used in investing activities	(23,769)	(34,196)	(84,471)
Cash flows from financing activities
Proceeds from long-term debt	0	6,163	58,771
Repayment of long-term debt	(14,513)	(477)	(1,368)
Dividends paid	(17,625)	(16,513)	(14,562)
Stock options exercised, other	(811)	1,048	804
Payments for repurchase on common stock	(5,859)	(7,276)	0
Excess tax benefit from stock option exercises	678	384	453
Purchase of noncontrolling interest in affiliates, net	0	0	(7,422)
Payment of acquisition-related liabilities	0	(226)	(4,709)
Distributions to noncontrolling affiliate shareholders	0	0	(1,806)
Net cash (used in) provided by financing activities	(38,130)	(16,897)	30,161
Effect of exchange rate changes on cash	(4,089)	(6,017)	(4,141)
Net increase (decrease) in cash and cash equivalents	7,765	16,322	(3,761)
Cash and cash equivalents at beginning of period	81,053	64,731	68,492
Cash and cash equivalents at end of period	88,818	81,053	64,731
Supplemental Cash Flow Information [Abstract]
Income Taxes Paid	25,043	20,996	22,713
Interest Paid	2,481	2,223	1,894
Other Noncash Investing And Financing Items [Abstract]
Change in accrued purchases of property, plant and equipment, net	$ 363	$ 209	$ (1,158)