Stock-Based Compensation (Details) (USD $)	3 Months Ended
Mar. 31, 2015 plan	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 900,000	$ 1,600,000
Number of share-based compensation plans	4imn_NumberOfShareBasedCompensationPlans
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0
Number of awards granted	2,700,000
Number of awards outstanding	5,500,000
Stock Appreciation Rights (SARs) \| Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of awards vested	50.00%
Number of average consecutive trading days required at trigger stock price	30 days
Minimum stock price required to trigger award vesting	$ 8
Stock Appreciation Rights (SARs) \| Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of awards vested	50.00%
Number of average consecutive trading days required at trigger stock price	30 days
Minimum stock price required to trigger award vesting	$ 12
Stock Incentive Plan 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	1,273,822

Number of Share-Based Compensation Plans

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Stock Price Trigger

+ References

No definition available.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Threshold Consecutive Trading Days

+ References

No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

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-Subparagraph (SAB TOPIC 14.F)

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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- Definition

Percentage of vesting of share-based compensation awards.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

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-Paragraph 2

-Subparagraph (c)(1)(i)

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

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