Business Overview (Details)	12 Months Ended
	Sep. 30, 2020 employee business_area location	Sep. 30, 2019
Concentration Risk [Line Items]
Number of market focus areas | business_area	3
Number of market core competencies | business_area	7
Number of employees (over) | employee	2,200
Customer Concentration | Revenue Concentration | Federal Government
Concentration Risk [Line Items]
Concentration risk percentage	98.00%
Customer Concentration | Revenue Concentration | VA
Concentration Risk [Line Items]
Concentration risk percentage	48.00%	57.00%
Customer Concentration | Revenue Concentration | HHS
Concentration Risk [Line Items]
Concentration risk percentage	45.00%	39.00%
United States
Concentration Risk [Line Items]
Number of locations in which the entity operates (more than) | location	30
Overseas
Concentration Risk [Line Items]
Number of locations in which the entity operates (more than) | location	1