Inventories - Schedule of Components of Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 56,101	$ 32,552
Work-in-process	300,831	312,953
Finished goods	52,167	50,011
Rotable assets	56,701	57,460
Total inventories	$ 465,800	$ 452,976	[1]

[1] As adjusted; refer to Note 1.