Goodwill and Intangible Assets - Finite Lived Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2019	Sep. 30, 2018
Finite-lived intangible assets
Gross Amount	$ 88,514	$ 86,237
Accumulated Amortization	(78,076)	(70,114)
Estimated amortization expense
2019	1,873
2020	4,871
2021	2,246
2022	1,020
2023	428
Total	$ 10,438
Non-compete agreements
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	0 years
Gross Amount	$ 0	83
Accumulated Amortization	$ 0	(83)
Client relations
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	2 years 6 months
Gross Amount	$ 54,483	54,639
Accumulated Amortization	$ (49,791)	(46,449)
Backlog
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	8 months 12 days
Gross Amount	$ 26,075	23,371
Accumulated Amortization	$ (23,623)	(20,007)
Trade names
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	2 years 7 months 6 days
Gross Amount	$ 7,956	8,144
Accumulated Amortization	$ (4,662)	$ (3,575)