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Business Overview - Narrative (Details) | 12 Months Ended
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Sep. 30, 2021 employee business_area location customer | Sep. 30, 2020
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 | 2,300 |
Number of largest customers | customer | 3 |
Customer Concentration | Revenue Concentration |  |
Concentration Risk [Line Items] |  |
Percent of total revenue | 100.00% | 100.00%
Customer Concentration | Revenue Concentration | Federal Government |  |
Concentration Risk [Line Items] |  |
Percent of total revenue | 99.00% |
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 |

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