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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
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The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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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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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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
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Number of share instruments newly issued under a share-based compensation plan.

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Stock-Based Compensation - Additional Information (Detail) $ in Millions				3 Months Ended		6 Months Ended
	May 17, 2017 Director shares	May 18, 2016 Director shares	May 11, 2015 Director shares	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($)
May Two Thousand Fifteen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock expense					$ 0.1		$ 0.3
May Two Thousand Sixteen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock expense				$ 0.1	$ 0.1	$ 0.2	$ 0.1
May Two Thousand Seventeen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock expense				0.1		$ 0.1
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation awards, requisite service period						3 years
Restricted Stock [Member] \| May Two Thousand Fifteen [Member] \| Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares of common stock issued \| shares			132,496
Number of non employee directors \| Director			7
Restricted Stock [Member] \| May Two Thousand Sixteen [Member] \| Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares of common stock issued \| shares		149,448
Number of non employee directors \| Director		3
Restricted Stock [Member] \| May Two Thousand Seventeen [Member] \| Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares of common stock issued \| shares	153,192
Number of non employee directors \| Director	3
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation awards, requisite service period						3 years
Unrecognized compensation cost				8.5		$ 8.5
Weighted average period for shares to vest						1 year
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost				7.0		$ 7.0
Weighted average period for shares to vest						2 years
Restricted Stock Issued to Directors [Member] \| May Two Thousand Seventeen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost				$ 0.3		$ 0.3
2014 Long-Term Incentive as Amended Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be issue \| shares				25,000,000		25,000,000
Number of shares are available for future grants \| shares				10,345,434		10,345,434