Revenue Recognition (Schedule of Consolidated Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 197,755	$ 183,727	$ 181,742	$ 185,113
Accounts receivable, net	223,176	202,675
Contract assets	57,447
Inventories	85,904	136,519
Income taxes prepaid and receivable	7,473	6,266
Prepaid expenses and other current assets	21,294	14,520
Total current assets	593,049	543,707
Property, plant and equipment, net	462,055	454,302	422,564
Intangibles, net	49,206	55,441
Goodwill	164,382	166,796	160,375
Deferred income taxes	62,622	68,648
Noncurrent receivable	45,061	32,811
Other assets	41,617	39,493
Total assets	1,417,992	1,361,198	$ 1,263,433
Current liabilities:
Notes and loans payable		262
Accounts payable	52,246	44,899
Accrued liabilities	129,030	105,914
Current maturities of long-term debt	1,224	1,799
Income taxes payable	6,806	8,643
Total current liabilities	189,306	161,517
Long-term debt	523,707	514,120
Other noncurrent liabilities	88,277	101,555
Deferred taxes and other liabilities	8,422	10,991
Total liabilities	809,712	788,183
Commitments and Contingencies
Shareholders' Equity
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid-in capital	430,555	428,423
Retained earnings	589,645	534,082
Accumulated items of other comprehensive income:
Translation adjustments	(115,976)	(87,318)
Pension and postretirement liability adjustments	(47,109)	(50,536)
Derivative valuation adjustment	4,697	1,953
Treasury stock (Class A), at cost; 8,431,335 shares in 2017	(256,603)	(256,876)
Total Company shareholders' equity	605,249	569,768
Noncontrolling interest	3,031	3,247
Total equity	608,280	573,015
Total liabilities and shareholders' equity	1,417,992	1,361,198
Common Class A [Member]
Shareholders' Equity
Common Stock	37	37
Common Class B [Member]
Shareholders' Equity
Common Stock	$ 3	3
As previously Reported [Member]
Current assets:
Cash and cash equivalents		183,727
Accounts receivable, net		202,675
Contract assets
Inventories		136,519
Income taxes prepaid and receivable		6,266
Prepaid expenses and other current assets		14,520
Total current assets		543,707
Property, plant and equipment, net		454,302
Intangibles, net		55,441
Goodwill		166,796
Deferred income taxes		68,648
Noncurrent receivable		32,811
Other assets		39,493
Total assets		1,361,198
Current liabilities:
Notes and loans payable		262
Accounts payable		44,899
Accrued liabilities		105,914
Current maturities of long-term debt		1,799
Income taxes payable		8,643
Total current liabilities		161,517
Long-term debt		514,120
Other noncurrent liabilities		101,555
Deferred taxes and other liabilities		10,991
Total liabilities		788,183
Commitments and Contingencies
Shareholders' Equity
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid-in capital		428,423
Retained earnings		534,082
Accumulated items of other comprehensive income:
Translation adjustments		(87,318)
Pension and postretirement liability adjustments		(50,536)
Derivative valuation adjustment		1,953
Treasury stock (Class A), at cost; 8,431,335 shares in 2017		(256,876)
Total Company shareholders' equity		569,768
Noncontrolling interest		3,247
Total equity		573,015
Total liabilities and shareholders' equity		1,361,198
As previously Reported [Member] | Common Class A [Member]
Shareholders' Equity
Common Stock		37
As previously Reported [Member] | Common Class B [Member]
Shareholders' Equity
Common Stock		3
Adjustments Increase/(decrease) [Member]
Current assets:
Cash and cash equivalents
Accounts receivable, net		8,486
Contract assets		47,415
Inventories		(48,583)
Income taxes prepaid and receivable
Prepaid expenses and other current assets
Total current assets		7,318
Property, plant and equipment, net
Intangibles, net
Goodwill
Deferred income taxes		2,889
Noncurrent receivable
Other assets		1,119
Total assets		11,326
Current liabilities:
Notes and loans payable
Accounts payable
Accrued liabilities		17,217
Current maturities of long-term debt
Income taxes payable
Total current liabilities		17,217
Long-term debt
Other noncurrent liabilities
Deferred taxes and other liabilities		52
Total liabilities		17,269
Commitments and Contingencies
Shareholders' Equity
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid-in capital
Retained earnings		(5,616)
Accumulated items of other comprehensive income:
Translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Treasury stock (Class A), at cost; 8,431,335 shares in 2017
Total Company shareholders' equity		(5,616)
Noncontrolling interest		(327)
Total equity		(5,943)
Total liabilities and shareholders' equity		11,326
Adjustments Increase/(decrease) [Member] | Common Class A [Member]
Shareholders' Equity
Common Stock
Adjustments Increase/(decrease) [Member] | Common Class B [Member]
Shareholders' Equity
Common Stock
Opening balance, as adjusted, January 1, 2018 [Member]
Current assets:
Cash and cash equivalents		183,727
Accounts receivable, net		211,161
Contract assets		47,415
Inventories		87,936
Income taxes prepaid and receivable		6,266
Prepaid expenses and other current assets		14,520
Total current assets		551,025
Property, plant and equipment, net		454,302
Intangibles, net		55,441
Goodwill		166,796
Deferred income taxes		71,537
Noncurrent receivable		32,811
Other assets		40,612
Total assets		1,372,524
Current liabilities:
Notes and loans payable		262
Accounts payable		44,899
Accrued liabilities		123,131
Current maturities of long-term debt		1,799
Income taxes payable		8,643
Total current liabilities		178,734
Long-term debt		514,120
Other noncurrent liabilities		101,555
Deferred taxes and other liabilities		11,043
Total liabilities		805,452
Commitments and Contingencies
Shareholders' Equity
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid-in capital		428,423
Retained earnings		528,466
Accumulated items of other comprehensive income:
Translation adjustments		(87,318)
Pension and postretirement liability adjustments		(50,536)
Derivative valuation adjustment		1,953
Treasury stock (Class A), at cost; 8,431,335 shares in 2017		(256,876)
Total Company shareholders' equity		564,152
Noncontrolling interest		2,920
Total equity		567,072
Total liabilities and shareholders' equity		1,372,524
Opening balance, as adjusted, January 1, 2018 [Member] | Common Class A [Member]
Shareholders' Equity
Common Stock		37
Opening balance, as adjusted, January 1, 2018 [Member] | Common Class B [Member]
Shareholders' Equity
Common Stock		$ 3