Goodwil and Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018
IntangibleAssets [Line Items]
Gross Carrying Amount	$ 41,625	$ 41,625
Accumulated Amortization	12,080	11,035
Intangible assets, net	29,545	30,590
Trademarks And Trade Names [Member]
IntangibleAssets [Line Items]
Gross Carrying Amount	5,084	5,084
Accumulated Amortization	941	831
Intangible assets, net	$ 4,143	$ 4,253
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]
Estimated Useful Lives	20 years	20 years
Gross Carrying Amount	$ 400	$ 400
Accumulated Amortization	106	101
Intangible assets, net	294	299
Customer Relationships [Member]
IntangibleAssets [Line Items]
Gross Carrying Amount	33,539	33,539
Accumulated Amortization	8,665	7,870
Intangible assets, net	$ 24,874	$ 25,669
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]
Estimated Useful Lives	1 year	1 year
Gross Carrying Amount	$ 378	$ 378
Accumulated Amortization	267	176
Intangible assets, net	$ 111	$ 202
Construction Contract Value [Member]
IntangibleAssets [Line Items]
Estimated Useful Lives	1 year	1 year
Gross Carrying Amount	$ 2,184	$ 2,184
Accumulated Amortization	2,098	2,056
Intangible assets, net	$ 86	$ 128