Common Stock Incentive Plan (Details) - 2012 Plan - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Plan disclosures
Plan term from the date of adoption	10 years
Share-based compensation costs recognized	$ 2.6	$ 2.6
Maximum
Plan disclosures
Authorized shares	3,985,734
Restricted Stock
Number of shares
Shares granted	141,139
Additional disclosures
Remaining unamortized share-based compensation expense	$ 19.5
Vesting period	5 years
Performance Shares
Additional disclosures
Awards vesting on the first and second January1 after the end of the three year performance period (as a percent)	50.00%
Performance Shares \| Executive officers
Number of shares
Shares granted	58,569
Restricted Stock Units
Number of shares
Shares granted	11,098
Additional disclosures
Vesting period	5 years
Performance Shares and Restricted Stock Units
Additional disclosures
Remaining unamortized share-based compensation expense	$ 6.2

Percentage of vesting of share-based compensation awards in specified period one.

No definition available.

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- Definition

This element represents the period of time from a share-based compensation plan's inception until the point at which no further common stock subject to options, stock purchase rights, stock appreciation rights, or SAR, and other awards may be granted under that specific plan.

+ 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 S99
-Paragraph 1
-Subparagraph (SAB TOPIC 14.F)
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-Topic 718
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-Paragraph 1
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-Name Staff Accounting Bulletin (SAB)
-Number Topic 14
-Section F

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Unrecognized cost of unvested share-based compensation awards.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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-Publisher FASB
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- 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.

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No definition available.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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