Revenue Recognition (Schedule of Consolidated Balance Sheets) (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 receivables	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; 8,418,620 shares in 2018 and 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 reported [Member]
Current assets:
Cash and cash equivalents	197,755
Accounts receivable, net	223,176
Contract assets	57,447
Inventories	85,904
Income taxes prepaid and receivable	7,473
Prepaid expenses and other current assets	21,294
Total current assets	593,049
Property, plant and equipment, net	462,055
Intangibles, net	49,206
Goodwill	164,382
Deferred income taxes	62,622
Noncurrent receivables	45,061
Other assets	41,617
Total assets	1,417,992
Current liabilities:
Notes and loans payable
Accounts payable	52,246
Accrued liabilities	129,030
Current maturities of long-term debt	1,224
Income taxes payable	6,806
Total current liabilities	189,306
Long-term debt	523,707
Other noncurrent liabilities	88,277
Deferred taxes and other liabilities	8,422
Total liabilities	809,712
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
Retained earnings	589,645
Accumulated items of other comprehensive income:
Translation adjustments	(115,976)
Pension and postretirement liability adjustments	(47,109)
Derivative valuation adjustment	4,697
Treasury stock (Class A), at cost; 8,418,620 shares in 2018 and 8,431,335 shares in 2017	(256,603)
Total Company shareholders' equity	605,249
Noncontrolling interest	3,031
Total equity	608,280
Total liabilities and shareholders' equity	1,417,992
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]
Current assets:
Cash and cash equivalents
Accounts receivable, net	5,578
Contract assets	(57,447)
Inventories	42,701
Income taxes prepaid and receivable
Prepaid expenses and other current assets
Total current assets	(9,168)
Property, plant and equipment, net
Intangibles, net
Goodwill
Deferred income taxes	(2,012)
Noncurrent receivables
Other assets	(1,256)
Total assets	(12,436)
Current liabilities:
Notes and loans payable
Accounts payable
Accrued liabilities	(16,454)
Current maturities of long-term debt
Income taxes payable
Total current liabilities	(16,454)
Long-term debt
Other noncurrent liabilities
Deferred taxes and other liabilities	(52)
Total liabilities	(16,506)
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	3,297
Accumulated items of other comprehensive income:
Translation adjustments	575
Pension and postretirement liability adjustments
Derivative valuation adjustment
Treasury stock (Class A), at cost; 8,418,620 shares in 2018 and 8,431,335 shares in 2017
Total Company shareholders' equity	3,872
Noncontrolling interest	198
Total equity	4,070
Total liabilities and shareholders' equity	(12,436)
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]
Current assets:
Cash and cash equivalents	197,755
Accounts receivable, net	228,754
Contract assets
Inventories	128,605
Income taxes prepaid and receivable	7,473
Prepaid expenses and other current assets	21,294
Total current assets	583,881
Property, plant and equipment, net	462,055
Intangibles, net	49,206
Goodwill	164,382
Deferred income taxes	60,610
Noncurrent receivables	45,061
Other assets	40,361
Total assets	1,405,556
Current liabilities:
Notes and loans payable
Accounts payable	52,246
Accrued liabilities	112,576
Current maturities of long-term debt	1,224
Income taxes payable	6,806
Total current liabilities	172,852
Long-term debt	523,707
Other noncurrent liabilities	88,277
Deferred taxes and other liabilities	8,370
Total liabilities	793,206
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
Retained earnings	592,942
Accumulated items of other comprehensive income:
Translation adjustments	(115,401)
Pension and postretirement liability adjustments	(47,109)
Derivative valuation adjustment	4,697
Treasury stock (Class A), at cost; 8,418,620 shares in 2018 and 8,431,335 shares in 2017	(256,603)
Total Company shareholders' equity	609,121
Noncontrolling interest	3,229
Total equity	612,350
Total liabilities and shareholders' equity	1,405,556
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