Revenue Recognition - Reimbursable Payroll Related and Other Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 138,649	$ 143,715	$ 439,402	$ 554,124
Shared service fees	250	370	964	1,076
Equity based compensation expense and related reimbursements	736	882	1,394	2,954
Reimbursable compensation and benefits
Disaggregation of Revenue [Line Items]
Revenue	13,749	13,583	40,077	40,868
Other client company reimbursable expenses
Disaggregation of Revenue [Line Items]
Revenue	$ 85,650	$ 85,689	$ 267,852	$ 257,088