Acquisitions (Narratives) (Details) - USD ($)		3 Months Ended								12 Months Ended
	Feb. 15, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired										$ 0	$ 87,110,000	$ 0
Sales		$ 275,707,000	$ 267,294,000	$ 263,759,000	$ 258,711,000	$ 245,836,000	$ 247,121,000	$ 247,347,000	$ 221,026,000	1,065,471,000	961,330,000	828,341,000
Proceeds from Previous Acquisition					$ 4,250,000					5,000,000	0	0
Goodwill		81,404,000				128,208,000				81,404,000	128,208,000	117,822,000
Payments to Acquire Property, Plant, and Equipment										$ 40,814,000	$ 44,362,000	$ 45,457,000
Effective Income Tax Rate Reconciliation, Percent										31.70%	356.50%	11.60%
Futura Industries [Member]
Business Acquisition [Line Items]
Business Combinations Accretion to Diluted Earnings Per Share		0.03								$ 0.12
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	$ 6,680,000
Percentage of outstanding equity interests acquired	100.00%
Business Combination Contract Price	$ 92,000,000
Business Combination, Consideration Transferred	87,000,000
Business Combinations Amount Deposited in Escrow - Earnout	5,000,000
Business Combination, Contingent Consideration, Asset, Current	4,300,000							5,000,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Asset								700,000
Business Combinations Purchase Price Allocated Net of Contingent Consideration	82,860,000
Goodwill, Purchase Accounting Adjustments								$ 100,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory	10,342,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets	240,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	32,662,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	(8,135,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 72,489,000
Tax Recovery Life of Goodwill for Amortization	15 years
Line of Credit Facility, Interest Rate During Period											3.00%
Effective Income Tax Rate Reconciliation, Percent											39.10%
Customer Relationships [Member] | Futura Industries [Member]
Business Acquisition [Line Items]
Purchased identifiable intangible assets, amortized over weighted average period	12 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 24,000,000
Trade Names [Member] | Futura Industries [Member]
Business Acquisition [Line Items]
Purchased identifiable intangible assets, amortized over weighted average period	13 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 6,700,000
Goodwill [Member] | Futura Industries [Member]
Business Acquisition [Line Items]
Goodwill	$ 10,371,000
Futura Industries [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue											$ 968,340,000	$ 904,877,000
Sales											71,000,000
Ongoing operations											8,200,000
Depreciation, Amortization and Accretion, Net											5,000,000
Payments to Acquire Property, Plant, and Equipment											2,500,000
Business Acquisition, Pro Forma Net Income (Loss)											$ 37,974,000	$ 27,805,000
Business Acquisition, Pro Forma Earnings Per Share, Basic											$ 1.15	$ 0.85
Business Acquisition, Pro Forma Earnings Per Share, Diluted											$ 1.15	$ 0.85
Other Assets and Deferred Charges [Member] | kaleo [Member]
Business Acquisition [Line Items]
Investment Owned, at Fair Value		$ 84,600,000				$ 54,000,000				$ 84,600,000	$ 54,000,000