Litigation, Commitments and Contingencies - Threatened Litigation (Details) $ in Millions		3 Months Ended
Mar. 16, 2018 USD ($) purchaser	Mar. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Accounts receivable sold		$ 1.2
Proceeds from sale of accounts receivable		$ 1.1
Repurchase of accounts receivable, term		5 months
Repurchase of accounts receivable, interest rate		2.00%
Subsequent Event \| Threatened Litigation \| Obligation to Repurchase Receivables Sold
Loss Contingencies [Line Items]
Number of accounts receivable purchasers with outstanding demands \| purchaser	2
Loss contingency, damages sought	$ 0.5

Number Of Accounts Receivable Purchasers With Outstanding Demands

No definition available.

Name:	imn_NumberOfAccountsReceivablePurchasersWithOutstandingDemands
Namespace Prefix:	imn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Repurchase Of Accounts Receivable, Interest Rate

+ References

No definition available.

+ Details

Name:	imn_RepurchaseOfAccountsReceivableInterestRate
Namespace Prefix:	imn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Repurchase of Accounts Receivable, Term

+ References

No definition available.

+ Details

Name:	imn_RepurchaseofAccountsReceivableTerm
Namespace Prefix:	imn_
Data Type:	xbrli:durationItemType
Balance Type:	na
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_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

+ Details

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

- Definition

Amount of derecognized financial assets from transactions which comprise an initial transfer and an agreement entered into in contemplation of the initial transfer resulting in retention of substantially all of the exposure to the economic return throughout the term of the transaction, at the date of derecognition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82924980&loc=SL51823488-111719

+ Details

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

- Definition

Amount, before counterparty netting, of cash proceeds received in transfers of derecognized financial assets from transactions which comprise an initial transfer and an agreement entered into in contemplation of the initial transfer resulting in retention of substantially all of the exposure to the economic return throughout the term of the transaction.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82924980&loc=SL51823488-111719

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationStatusAxis=us-gaap_ThreatenedLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_ObligationToRepurchaseReceivablesSoldMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: