Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Statement of Financial Position [Abstract]
Cash and cash equivalents	$ 27,281	$ 53,577
Restricted Cash	4,813	0
Accounts receivable	214,948	213,016
Retainage	41,821	40,878
Inventories	33,298	24,889
Costs and estimated earnings in excess of billings	23,836	29,937
Prepaid expenses and other current assets	12,878	9,153
Total current assets	358,875	371,450
Property and equipment, net	29,164	24,589
Goodwill	86,449	53,763
Intangible assets, net	62,823	39,357
Deferred tax assets	29,760	33,803
Operating right of use assets	36,606	31,786
Other non-current assets	5,693	5,780
Total assets	609,370	560,528
Accounts payable and accrued expenses	184,270	186,710
Billings in excess of costs and estimated earnings	64,731	55,739
Total current liabilities	249,001	242,449
Long-term debt	14,495	217
Operating long-term lease liabilities	23,907	20,530
Other non-current liabilities	13,912	12,215
Total liabilities	301,315	275,411
Noncontrolling interest	12,593	1,804
Preferred stock, value	0	0
Common stock, value	220	220
Treasury stock, value	(24,984)	(24,499)
Additional paid-in capital	201,219	200,587
Retained earnings	119,007	107,005
Total stockholders' equity	295,462	283,313
Total liabilities and stockholders' equity	$ 609,370	$ 560,528