Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Sep. 30, 2018 Reporting_Unit
Product Information [Line Items]
Number of identified reporting units	4
Income Approache [Member]
Product Information [Line Items]
Percentage of estimated fair value of reporting units	75.00%
Market Approache [Member]
Product Information [Line Items]
Percentage of estimated fair value of reporting units	25.00%
Minimum
Product Information [Line Items]
Percentage of not collected receivable until completion to total contract value	5.00%
Maximum
Product Information [Line Items]
Percentage of not collected receivable until completion to total contract value	10.00%