Goodwill and Intangible Assets - Finite Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Oct. 01, 2017
Finite-lived intangible assets
Gross Amount	$ 82,232		$ 118,995
Accumulated Amortization	(57,699)		(92,307)
Amortization expense	4,600	$ 5,900
Estimated amortization expense
2018	12,413
2019	7,027
2020	2,799
2021	1,654
2022	411
Beyond	229
Total	$ 24,533
Non-compete agreements
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	0 years
Gross Amount	$ 85		495
Accumulated Amortization	$ (85)		(493)
Client relations
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	2 years 9 months 18 days
Gross Amount	$ 54,940		90,297
Accumulated Amortization	$ (41,700)		(75,074)
Backlog
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	1 year 1 month 6 days
Gross Amount	$ 21,896		21,518
Accumulated Amortization	$ (13,530)		(13,301)
Trade names
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)	3 years
Gross Amount	$ 5,311		6,685
Accumulated Amortization	$ (2,384)		$ (3,439)