Goodwil and Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017
IntangibleAssets [Line Items]
Gross Carrying Amount	$ 41,083	$ 40,969
Accumulated Amortization	11,568	9,556
Intangible assets, net	29,515	31,413
Trademarks And Trade Names [Member]
IntangibleAssets [Line Items]
Gross Carrying Amount	4,643	4,643
Accumulated Amortization	622	440
Intangible assets, net	$ 4,021	$ 4,203
Trademarks And Trade Names [Member] | Maximum [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	20 years	20 years
Trademarks And Trade Names [Member] | Minimum [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	5 years	5 years
Technical Library [Member]
IntangibleAssets [Line Items]
Gross Carrying Amount	$ 400	$ 400
Accumulated Amortization	91	81
Intangible assets, net	$ 309	$ 319
Technical Library [Member] | Maximum [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	20 years	20 years
Customer Relationships [Member]
IntangibleAssets [Line Items]
Gross Carrying Amount	$ 31,229	$ 31,115
Accumulated Amortization	6,234	4,741
Intangible assets, net	$ 24,995	$ 26,374
Customer Relationships [Member] | Maximum [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	15 years	15 years
Customer Relationships [Member] | Minimum [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	6 years	6 years
Order Backlog [Member]
IntangibleAssets [Line Items]
Gross Carrying Amount	$ 2,412	$ 2,412
Accumulated Amortization	2,412	2,130
Intangible assets, net	$ 0	$ 282
Order Backlog [Member] | Maximum [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	1 year	1 year
Construction Contract Value [Member]
IntangibleAssets [Line Items]
Gross Carrying Amount	$ 2,399	$ 2,399
Accumulated Amortization	2,209	2,164
Intangible assets, net	$ 190	$ 235
Construction Contract Value [Member] | Maximum [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	1 year	1 year