Capital Stock and Derivative Instruments - Summary of Company's Restricted Share Award Activity (Detail) - Restricted stock award [Member] - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
Jun. 01, 2017	Jun. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Restricted Stock Awards Outstanding, Beginning balance			6,380,800	6,168,035	2,343,245
Number of Restricted Stock Awards Outstanding, Restricted stock awards granted	333,332	212,765	333,332	212,765	3,824,790
Number of Restricted Stock Awards Outstanding, Ending balance			6,714,132	6,380,800	6,168,035
Weighted Average Grant Date Fair Value, Beginning balance			$ 2.1306	$ 2.1230	$ 1.1023
Weighted Average Grant Date Fair Value, Restricted stock awards granted			1.2000	2.3500	2.7486
Weighted Average Grant Date Fair Value, Ending balance			$ 2.0844	$ 2.1306	$ 2.1230
Aggregate Fair Value, Beginning balance			$ 13,595	$ 13,095	$ 2,582
Aggregate Fair Value, Restricted stock awards granted			400	500	10,513
Aggregate Fair Value, Ending balance			$ 13,995	$ 13,595	$ 13,095

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).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued 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

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ 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 (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ 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 (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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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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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options aggregate fair value outstanding.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options grants in period aggregate fair value.

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