Revenue Recognition - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
Dec. 31, 2021	Dec. 31, 2022	Sep. 30, 2021	Sep. 30, 2020
Fire & Emergency
Disaggregation Of Revenue [Line Items]
Impairment losses on contract assets	$ 0	$ 0	$ 0	$ 0
Interest charges on customer advances	$ 4,600,000	$ 23,400,000	$ 17,200,000	$ 15,600,000
Customer Concentration Risk \| Sales Revenue, Net \| Defense \| DoD
Disaggregation Of Revenue [Line Items]
Concentration Risk, Percentage	93.00%	95.00%	95.00%	96.00%

Amount of impairment loss for asset recognized from cost incurred to obtain or fulfill contract with customer.

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-Publisher FASB
-Name Accounting Standards Codification
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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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No definition available.

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The interest expense recognized during the period on customer deposits or security deposits held in interest bearing accounts.

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