Net Receivables - Allowance for doubtful accounts (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Dec. 31, 2015	Mar. 31, 2015	Mar. 31, 2014
Reconciliation of the changes in ATK's allowance for doubtful accounts
Balance at the beginning of the year	$ 4,692	$ 4,891	$ 4,801
Expense	12	599	609
Write-offs	(3,737)	(17)	(626)
Other adjustments	61	(781)	107
Balance at the end of the year	$ 1,028	$ 4,692	$ 4,891