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Significant Accounting Policies (Details) $ in Billions | 12 Months Ended
--- | ---
Sep. 30, 2015 USD ($) item | Sep. 30, 2014 USD ($) | Sep. 30, 2013 USD ($)
Fiscal Year |  |  |
Length of Fiscal Year | 364 days | 371 days | 364 days
Revenue Recognition |  |  |
Other direct costs | $ | $ 8.3 | $ 3.5 | $ 3.2
Number of cost reimbursable contracts | 2 |  |
Cost-Plus Contracts |  |  |
Number of major types of cost-plus contracts the Company enters into | 2 |  |
Fixed Price Contracts |  |  |
Number of types of fixed price contracts | 2 |  |
Pension Plans |  |  |
Amortization period of the difference between actual return and expected return | 5 years |  |
Specified percentage to be exceeded for amortization of cumulative, net unrecognized gains or losses (as a percent) | 10.00% |  |
Minimum |  |  |
Fiscal Year |  |  |
Fiscal year period | 364 days |  |
Property and Equipment |  |  |
Estimated useful lives for equipment furniture and fixtures | 3 years |  |
Maximum |  |  |
Fiscal Year |  |  |
Fiscal year period | 371 days |  |
Property and Equipment |  |  |
Estimated useful lives for equipment furniture and fixtures | 10 years |  |

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