v3.8.0.1

Long-term Debt - Senior Notes (Details) - USD ($)	Apr. 01, 2018	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Subsidiary guarantors percentage owned	100.00%
Senior Notes \| 5.50% Senior Notes due 2023
Debt Instrument [Line Items]
Debt instrument, face amount		$ 400,000,000
Interest rate		5.50%
Senior Notes \| 5.25% Senior Notes due 2021
Debt Instrument [Line Items]
Debt instrument, face amount			$ 300,000,000
Interest rate			5.25%

The parent's ownership percentage of the subsidiaries that are guarantors of the entity's debt.

+ References

No definition available.

+ Details

Name:	atk_SubsidiaryGuarantorsPercentageOwned
Namespace Prefix:	atk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=atk_SeniorNotes5.50due2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=atk_SeniorNotes5.25PercentDue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

ORBITAL ATK, INC. 10-Q