Accelerated Delivery Notice Period

No definition available.

Name:	atw_AcceleratedDeliveryNoticePeriod
Namespace Prefix:	atw_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Impairment of Long-Lived Assets to be Disposed of, Net of Tax

+ References

No definition available.

+ Details

Name:	atw_ImpairmentofLongLivedAssetstobeDisposedofNetofTax
Namespace Prefix:	atw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Insurance Recoveries Effect on Earnings Per Share Diluted, after Tax

+ References

No definition available.

+ Details

Name:	atw_InsuranceRecoveriesEffectonEarningsPerShareDilutedafterTax
Namespace Prefix:	atw_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Insurance Recoveries, Net of Tax

+ References

No definition available.

+ Details

Name:	atw_InsuranceRecoveriesNetofTax
Namespace Prefix:	atw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of assets held-for-sale that are not part of a disposal group.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 15
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6390208&loc=d3e400-110220

+ Details

Name:	us-gaap_AssetsHeldForSaleNotPartOfDisposalGroup
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfPropertyPlantEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

After tax earnings per share or per unit impact arising from asset impairment.

+ References

No definition available.

+ Details

Name:	us-gaap_ImpairmentEffectOnEarningsPerShareAfterTax
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2611-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

Name:	us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount recovered from insurance. These recoveries reduce costs and losses that are reported as a separate line item under operating expenses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_InsuranceRecoveries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The minimum amount the entity agreed to spend under the long-term purchase commitment.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow from construction costs to date on capital projects that have not been completed and assets being constructed that are not ready to be placed into service.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsForConstructionInProcess
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atw_AtwoodFalconMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_EquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_InventoriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atw_AtwoodHunterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atw_AtwoodOspreyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atw_AtwoodSouthernCrossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atw_AtwoodAdmiralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=us-gaap_CapitalAdditionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherCommitmentsAxis=atw_FinalPaymentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=atw_AtwoodArcherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Property and Equipment - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended				6 Months Ended
	Dec. 31, 2015	Dec. 17, 2015	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2016	Mar. 31, 2015
Property, Plant and Equipment
Asset impairment			$ 708		$ 0		$ 65,432	$ 60,777
(Gain) loss on sale of equipment			(77)		$ (5,529)		(77)	$ (15,335)
Atwood Falcon
Property, Plant and Equipment
Asset impairment			700	$ 64,700			65,432
Long lived assets held for sale			$ 1,300				1,300
Impairment, net of tax				$ 64,700
Impairment effect on earnings per share, after tax (in dollars per share)				$ 1.00
Atwood Falcon \| Equipment
Property, Plant and Equipment
Asset impairment				$ 53,000
Atwood Falcon \| Inventory
Property, Plant and Equipment
Asset impairment				11,700
Atwood Hunter
Property, Plant and Equipment
Asset impairment						$ 60,800
Impairment, net of tax						$ 56,100	$ 5,500
Impairment effect on earnings per share, after tax (in dollars per share)						$ 0.86	$ 0.08
(Gain) loss on sale of equipment							$ (5,500)
Atwood Hunter \| Equipment
Property, Plant and Equipment
Asset impairment						$ 48,000
Atwood Hunter \| Inventory
Property, Plant and Equipment
Asset impairment						$ 8,400
Atwood Osprey
Property, Plant and Equipment
Insurance recoveries				18,000
Insurance recoveries, net of tax				$ 18,000
Insurance recoveries effect on earnings per share, after tax (in dollars per share)				$ 0.28
Atwood Southern Cross
Property, Plant and Equipment
Impairment, net of tax							$ 7,100
Impairment effect on earnings per share, after tax (in dollars per share)							$ 0.11
(Gain) loss on sale of equipment							$ (8,000)
Atwood Admiral
Property, Plant and Equipment
Accelerated delivery notice period							45 days
Atwood Admiral \| Capital Addition Purchase Commitments
Property, Plant and Equipment
Payments for construction projects	$ 50,000
Atwood Admiral \| Capital Addition Purchase Commitments \| Final Payment
Property, Plant and Equipment
Commitments on drilling units under construction		$ 93,900
Atwood Archer
Property, Plant and Equipment
Accelerated delivery notice period							45 days
Atwood Archer \| Capital Addition Purchase Commitments
Property, Plant and Equipment
Payments for construction projects	$ 50,000
Atwood Archer \| Capital Addition Purchase Commitments \| Final Payment
Property, Plant and Equipment
Commitments on drilling units under construction		$ 305,900