Revenue Recognition (Schedule of Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 151,426	$ 183,727	$ 143,333	$ 181,742
Accounts receivable, net	248,538	202,675
Contract assets	42,895
Inventories	100,034	136,519
Income taxes prepaid and receivable	6,132	6,266
Prepaid expenses and other current assets	18,675	14,520
Total current assets	567,700	543,707
Property, plant and equipment, net	459,388	454,302
Intangibles, net	53,881	55,441
Goodwill	168,311	166,796
Income taxes receivable and deferred	70,174	68,648
Noncurrent receivables	35,338	32,811
Other assets	45,543	39,493
Total assets	1,400,335	1,361,198
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable	226	262
Accounts payable	45,694	44,899
Accrued liabilities	122,103	105,914
Current maturities of long-term debt	1,821	1,799
Income taxes payable	5,182	8,643
Total current liabilities	175,026	161,517
Long-term debt	518,656	514,120
Other noncurrent liabilities	100,170	101,555
Deferred taxes and other liabilities	11,339	10,991
Total liabilities	805,191	788,183
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital	428,859	428,423
Retained earnings	533,759	534,082
Accumulated items of other comprehensive income:
Translation adjustments	(69,672)	(87,318)
Pension and postretirement liability adjustments	(50,549)	(50,536)
Derivative valuation adjustment	6,433	1,953
Treasury stock (Class A), at cost 8,431,335 shares in 2018 and 2017	(256,876)	(256,876)
Total Company shareholders' equity	591,994	569,768
Noncontrolling interest	3,150	3,247
Total equity	595,144	573,015
Total liabilities and shareholders' equity	1,400,335	1,361,198
Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock	37	37
Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock	3	$ 3
As reported [Member]
ASSETS
Cash and cash equivalents	151,426
Accounts receivable, net	248,538
Contract assets	42,895
Inventories	100,034
Income taxes prepaid and receivable	6,132
Prepaid expenses and other current assets	18,675
Total current assets	567,700
Property, plant and equipment, net	459,388
Intangibles, net	53,881
Goodwill	168,311
Income taxes receivable and deferred	70,174
Noncurrent receivables	35,338
Other assets	45,543
Total assets	1,400,335
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable	226
Accounts payable	45,694
Accrued liabilities	122,103
Current maturities of long-term debt	1,821
Income taxes payable	5,182
Total current liabilities	175,026
Long-term debt	518,656
Other noncurrent liabilities	100,170
Deferred taxes and other liabilities	11,339
Total liabilities	805,191
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital	428,859
Retained earnings	533,759
Accumulated items of other comprehensive income:
Translation adjustments	(69,672)
Pension and postretirement liability adjustments	(50,549)
Derivative valuation adjustment	6,433
Treasury stock (Class A), at cost 8,431,335 shares in 2018 and 2017	(256,876)
Total Company shareholders' equity	591,994
Noncontrolling interest	3,150
Total equity	595,144
Total liabilities and shareholders' equity	1,400,335
As reported [Member] | Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock	37
As reported [Member] | Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock	3
Adjustments to reverse effects of ASC 606 [Member]
ASSETS
Cash and cash equivalents
Accounts receivable, net	(21,720)
Contract assets	(42,895)
Inventories	53,752
Income taxes prepaid and receivable
Prepaid expenses and other current assets
Total current assets	(10,863)
Property, plant and equipment, net
Intangibles, net
Goodwill
Income taxes receivable and deferred	(1,155)
Noncurrent receivables
Other assets	(1,256)
Total assets	(13,274)
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable
Accounts payable
Accrued liabilities	(17,624)
Current maturities of long-term debt
Income taxes payable
Total current liabilities	(17,624)
Long-term debt
Other noncurrent liabilities
Deferred taxes and other liabilities	(51)
Total liabilities	(17,675)
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Retained earnings	4,439
Accumulated items of other comprehensive income:
Translation adjustments	(308)
Pension and postretirement liability adjustments
Derivative valuation adjustment
Treasury stock (Class A), at cost 8,431,335 shares in 2018 and 2017
Total Company shareholders' equity	4,131
Noncontrolling interest	270
Total equity	4,401
Total liabilities and shareholders' equity	(13,274)
Adjustments to reverse effects of ASC 606 [Member] | Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock
Adjustments to reverse effects of ASC 606 [Member] | Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock
As adjusted to exclude adoption of ASC 606 [Member]
ASSETS
Cash and cash equivalents	151,426
Accounts receivable, net	226,818
Contract assets
Inventories	153,786
Income taxes prepaid and receivable	6,132
Prepaid expenses and other current assets	18,675
Total current assets	556,837
Property, plant and equipment, net	459,388
Intangibles, net	53,881
Goodwill	168,311
Income taxes receivable and deferred	69,019
Noncurrent receivables	35,338
Other assets	44,287
Total assets	1,387,061
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable	226
Accounts payable	45,694
Accrued liabilities	104,479
Current maturities of long-term debt	1,821
Income taxes payable	5,182
Total current liabilities	157,402
Long-term debt	518,656
Other noncurrent liabilities	100,170
Deferred taxes and other liabilities	11,288
Total liabilities	787,516
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital	428,859
Retained earnings	538,198
Accumulated items of other comprehensive income:
Translation adjustments	(69,980)
Pension and postretirement liability adjustments	(50,549)
Derivative valuation adjustment	6,433
Treasury stock (Class A), at cost 8,431,335 shares in 2018 and 2017	(256,876)
Total Company shareholders' equity	596,125
Noncontrolling interest	3,420
Total equity	599,545
Total liabilities and shareholders' equity	1,387,061
As adjusted to exclude adoption of ASC 606 [Member] | Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock	37
As adjusted to exclude adoption of ASC 606 [Member] | Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock	$ 3