Restructuring - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended			12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	[1]	Sep. 30, 2020	Sep. 30, 2019	[1]	Mar. 31, 2021
Restructuring Cost And Reserve [Line Items]
Restructuring	$ 13,237	$ 5,782		$ 28,676	$ 8,746
Systems & Support [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring				4,536
Aerospace Structures [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring				17,698
Aerospace Structures [Member] | Facility Closures [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring				13,097
Corporate Headquarters [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring				$ 6,442
Minimum [Member] | Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Consulting and severance costs							$ 32,000
Maximum [Member] | Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Consulting and severance costs							$ 34,000

[1] As adjusted; refer to Note 1.