Acquisitions (Narratives) (Details) - USD ($)	3 Months Ended									12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Jan. 31, 2017
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue										$ 839,419,000	$ 777,847,000
Business Combination, Contingent Consideration, Liability, Current										14,103,000
Net sales:										839,419,000	637,123,000	$ 597,103,000
Net income (loss)	$ 8,466,000	$ (10,565,000)	$ 12,508,000	$ 11,656,000	$ (4,738,000)	[1]	$ 505,000	$ 6,816,000	$ 6,401,000
Severance Costs										$ 4,163,000
Estimated useful life										18 years
Long-term Debt	$ 363,318,000				$ 421,319,000					$ 363,318,000	$ 421,319,000
Common Stock, Shares, Issued	23,045,479				22,565,613					23,045,479	22,565,613
Voting common stock: 50,000,000 shares authorized; 23,045,479 and 22,565,613 shares issued and outstanding	$ 230,000				$ 226,000					$ 230,000	$ 226,000
Business Acquisition, Pro Forma Net Income (Loss)											$ 20,699,000
Business Acquisition, Pro Forma Earnings Per Share, Basic											$ 0.92
Business Acquisition, Pro Forma Earnings Per Share, Diluted											$ 0.91
Engineered drawings
Business Acquisition [Line Items]
Estimated useful life										6 years
Customer relationships
Business Acquisition [Line Items]
Estimated useful life										18 years
Inventories [Member]
Business Acquisition [Line Items]
Amortization										$ 8,852,000
Ergomatic Products LLC [Member]
Business Acquisition [Line Items]
Working capital	212,000									212,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	246,000									246,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	717,000									717,000
Business Combination, Consideration Transferred, Other											$ 587,000
Restricted Cash and Cash Equivalents, Current	294,000									294,000
Liabilities											588,000
Ergomatic Products LLC [Member] | Patents [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	677,000									677,000
STAHL [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current											14,103,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	30,473,000									30,473,000
Working capital	18,593,000									18,593,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	14,234,000									14,234,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	143,039,000									143,039,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets	233,000									233,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	75,162,000									75,162,000
Business Acquisition Purchase Price Allocation Total Allocated	248,246,000									248,246,000
Business Combination, Consideration Transferred, Other										217,773,000
Net sales:										173,166,000	24,682,000
Net income (loss)										18,553,000	$ (6,022,000)
Annual sales of acquired entity										170,000,000
Goodwill	150,386,000									150,386,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles										64,000
Identifiable intangible assets acquired	(33,550,000)									(33,550,000)
Purchases of businesses, net of cash acquired										8,454,000
Business Combination, Integration Related Costs										8,763,000
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000									100,000,000			$ 545,000,000
Long-term Debt	$ 545,000,000									$ 545,000,000
Common Stock, Shares, Issued	2,273,000									2,273,000
Shares Issued, Price Per Share	$ 22.00									$ 22.00
Voting common stock: 50,000,000 shares authorized; 23,045,479 and 22,565,613 shares issued and outstanding	$ 50,000,000									$ 50,000,000
STAHL [Member] | Customer relationships
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	120,220,000									120,220,000
STAHL [Member] | Trademarks and Trade Names
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	18,191,000									18,191,000
STAHL [Member] | Backlog
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	1,968,000									1,968,000
STAHL [Member] | Patents [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	2,660,000									2,660,000
Maximum
Business Acquisition [Line Items]
Long-term Debt	$ 445,000,000									$ 445,000,000

[1] 19. Selected Quarterly Financial Data (Unaudited)Below is selected quarterly financial data for fiscal 2018 and 2017: Three Months Ended June 30, 2017 September 30, 2017 December 31, 2017 March 31, 2018Net sales $203,726 $212,828 $208,725 $214,140Gross profit 69,308 71,619 69,045 74,602Income (loss) from operations 20,015 19,587 14,173 16,324Net income (loss) $11,656 $12,508 $(10,565) $8,466 Net income (loss) per share – basic $0.52 $0.55 $(0.46) $0.37 Net income (loss) per share – diluted $0.51 $0.54 $(0.46) $0.36 Three Months Ended June 30, 2016 September 30, 2016 December 31, 2016 March 31, 2017Net sales $149,013 $151,925 $152,497 $183,688Gross profit 48,047 49,729 44,821 50,335Income from operations 11,201 12,619 5,317 (3,164)Net income (loss) $6,401 $6,816 $505 $(4,738) Net income (loss) per share – basic $0.32 $0.34 $0.02 $(0.22) Net income (loss) per share – diluted $0.32 $0.33 $0.02 $(0.22)