Reportable Segments - Financial Information (Details) $ in Thousands	3 Months Ended
	Dec. 30, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($)
Financial information regarding reportable segments
Number of renamed reportable segments | segment	2
Revenue	$ 717,431	$ 759,749
Income from operations	55,711	48,589
Total Assets	1,834,889		$ 1,959,421
GSG
Financial information regarding reportable segments
Revenue	717,431
CIG
Financial information regarding reportable segments
Revenue	759,749
Operating segment | GSG
Financial information regarding reportable segments
Revenue	411,971	442,772
Income from operations	37,413	39,125
Total Assets	495,343		468,010
Operating segment | CIG
Financial information regarding reportable segments
Revenue	317,793	331,513
Income from operations	27,099	21,294
Total Assets	441,829		478,197
Operating segment | RCM
Financial information regarding reportable segments
Revenue	1,453	6,807
Income from operations	4	(1,158)
Total Assets	24,185		25,683
Elimination of inter-segment revenue
Financial information regarding reportable segments
Revenue	(13,786)	(21,343)
Corporate
Financial information regarding reportable segments
Income from operations	(8,805)	$ (10,672)
Total Assets	$ 873,532		$ 987,531