Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018
Statement of Financial Position [Abstract]
Cash and cash equivalents	$ 13,104	$ 26,247
Accounts receivable	176,527	151,578
Retainage	27,358	24,312
Inventories	24,350	20,966
Costs and estimated earnings in excess of billings	34,807	31,446
Prepaid expenses and other current assets	8,876	8,144
Total current assets	285,022	262,693
Property and equipment, net	26,410	25,364
Goodwill	50,622	50,702
Intangible assets, net	27,535	30,590
Deferred tax assets	43,424	46,580
Other non-current assets	5,351	6,065
Total assets	438,364	421,994
Accounts payable and accrued expenses	150,406	130,591
Billings in excess of costs and estimated earnings	35,859	33,826
Total current liabilities	186,265	164,417
Long-term debt	9,915	29,564
Other non-current liabilities	1,926	4,374
Total liabilities	198,106	198,355
Noncontrolling interest	3,245	3,232
Preferred stock, value	0	0
Common stock, value	220	220
Treasury stock, value	(11,357)	(8,937)
Additional paid-in capital	192,389	196,810
Retained earnings	55,761	32,314
Total stockholders' equity	237,013	220,407
Total liabilities and stockholders' equity	$ 438,364	$ 421,994