Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Statement of Financial Position [Abstract]
Cash and cash equivalents	$ 37,520	$ 53,577
Restricted Cash	4,813	0
Accounts receivable	208,784	213,016
Retainage	36,806	40,878
Inventories	38,908	24,889
Costs and estimated earnings in excess of billings	24,239	29,937
Prepaid expenses and other current assets	14,692	9,153
Total current assets	365,762	371,450
Property and equipment, net	28,731	24,589
Goodwill	75,327	53,763
Intangible assets, net	73,325	39,357
Deferred tax assets	25,531	33,803
Operating right of use assets	40,372	31,786
Other non-current assets	6,604	5,780
Total assets	615,652	560,528
Accounts payable and accrued expenses	191,328	186,710
Billings in excess of costs and estimated earnings	60,257	55,739
Total current liabilities	251,585	242,449
Long-term debt	140	217
Operating long-term lease liabilities	26,923	20,530
Other non-current liabilities	14,840	12,215
Total liabilities	293,488	275,411
Noncontrolling interest	13,629	1,804
Preferred stock, value	0	0
Common stock, value	220	220
Treasury stock, value	(23,639)	(24,499)
Additional paid-in capital	200,732	200,587
Retained earnings	131,222	107,005
Total stockholders' equity	308,535	283,313
Total liabilities and stockholders' equity	$ 615,652	$ 560,528