Goodwill and Intangible Assets (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017
Goodwill [Line Items]
Amortization of intangibles	$ 3,908,000	$ 1,765,000	$ 11,547,000	$ 5,280,000
Goodwill	341,619,000		341,619,000			$ 319,299,000
Estimated amortization expense in 2018	15,000,000		15,000,000
Estimated amortization expense in 2019	15,000,000		15,000,000
Estimated amortization expense in 2020	15,000,000		15,000,000
Estimated amortization expense in 2021	15,000,000		15,000,000
Goodwill, Impaired, Accumulated Impairment Loss	107,000,000		107,000,000
Indefinite-Lived Trade Names	48,313,000		48,313,000
Rest of Products [Member]
Goodwill [Line Items]
Goodwill	331,930,000		331,930,000			309,744,000
Duff Norton Group [Member]
Goodwill [Line Items]
Goodwill	$ 9,689,000		$ 9,689,000			$ 9,555,000
Scenario, Forecast [Member]
Goodwill [Line Items]
Amortization of intangibles					$ 15,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					18 years
Scenario, Forecast [Member] | Trademark
Goodwill [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					17 years
Scenario, Forecast [Member] | Customer relationships
Goodwill [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					18 years
Scenario, Forecast [Member] | Patented Technology [Member]
Goodwill [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					18 years
Scenario, Forecast [Member] | Other Intangible Assets [Member]
Goodwill [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					6 years