Percentage of performance award grant in period.

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- Definition

Period for beginning of vesting.

+ References

No definition available.

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- Definition

Settlement percentage of common shares.

+ References

No definition available.

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- Definition

Settlement percentage of restricted stock units.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options target.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options target threshold.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award vesting ratio.

+ References

No definition available.

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- Definition

Share-based compensation arrangement by share-based payment award, vesting share price.

+ References

No definition available.

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- Definition

Share based compensation, restrictions lapsing percentage.

+ 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.

+ References

No definition available.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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- Definition

General descriptive information regarding an arrangement under which employees and directors receive: (a) awards of equity shares, equity share options, or other equity instruments; or (b) the entity incurs liabilities to them: (1) in amounts based, at least in part, on the price of the entity's shares or other equity instruments; or (2) that require or may require settlement by issuance of the entity's shares. Such an arrangement is usually provided to employees and directors to compensate them, provide performance incentives to them, and to attract or retain their services. May also include pertinent information particular to a plan that is not elsewhere specified in the taxonomy.

+ 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)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901

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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

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

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- Definition

Date the equity-based award expires, in CCYY-MM-DD format.

+ References

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- Definition

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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- 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

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

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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

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- Definition

Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

+ References

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-Publisher FASB
-Name Accounting Standards Codification
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Stock-Based Compensation Plans and Employee Benefits - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class Of Stock [Line Items]
Share-based payments award, number of shares available for grant	5,500,000
Number of Options, Granted	154,000	633,000	557,000
2016 VSEP [Member]
Class Of Stock [Line Items]
Vesting period	7 years
Compensation fully earned and vested description	Awards under the 2016 VSEP, if earned, may result in the granting of common shares of the Company and time-vested RSUs to participants on future measurement dates based on a performance period beginning on February 9, 2016 and ending on December 31, 2018 (the “Performance Period”). As a result, in general, the total compensation available to participants under the 2016 VSEP, if any, will be fully earned only after approximately seven years (the Performance Period and the final four-year, time-based vesting period for RSUs).
Settlement percentage of common shares	20.00%
Settlement percentage of restricted stock units	80.00%
Expected lapse percentage	20.00%
Minimum [Member] \| 2016 VSEP [Member]
Class Of Stock [Line Items]
Share price for vesting		$ 17.41
Maximum [Member] \| 2016 VSEP [Member]
Class Of Stock [Line Items]
Share price for vesting	$ 25.35
Stock options [Member]
Class Of Stock [Line Items]
Contractual term of stock options, Maximum	10 years
Vesting period	3 years
Portion of increments granted for stock options	one-third
Term of increment grant	one year after the date of grant.
Total unrecognized compensation cost granted	$ 0.3
Term of recognition of unrecognized stock option compensation cost	1 year 4 months 24 days
RSUs [Member]
Class Of Stock [Line Items]
Restricted common shares	700,000	500,000
Restricted Stock [Member]
Class Of Stock [Line Items]
Total unrecognized compensation cost granted	$ 11.3
Term of recognition of unrecognized stock option compensation cost	2 years 1 month 6 days
Restricted common shares			200,000
Weighted-average fair value of the restricted stock	$ 13.86
Common shares issued	100,000	100,000	100,000
Restricted Stock [Member] \| Minimum [Member]
Class Of Stock [Line Items]
Vesting period	3 years
Weighted-average fair value of the restricted stock	$ 8.78
Restricted Stock [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Vesting period	4 years
Weighted-average fair value of the restricted stock	$ 19.26
Performance-Based Restricted Share Units (PRSUs) [Member]
Class Of Stock [Line Items]
Performance-based restricted share units, description	In 2017, the Board of Directors approved grants to the chief executive officer, chief operating officer and chief financial officer, PRSUs covering a “target” number of shares, subject to a performance period beginning on March 1, 2017, for one-year, two-year and three-year periods.
Performance-based restricted share units, fair value	$ 3.9
Share-based compensation arrangement by share-based payment award, award amortized period	Feb. 28, 2020
Performance-Based Restricted Share Units (PRSUs) [Member] \| Minimum [Member]
Class Of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, target	0.00%
Performance-Based Restricted Share Units (PRSUs) [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, target threshold	200.00%
Time-based Vesting [Member] \| 2016 VSEP [Member]
Class Of Stock [Line Items]
Vesting period	4 years
Performance Awards [Member] \| 2016 VSEP [Member]
Class Of Stock [Line Items]
Aggregate percentage of performance awards	1.4909%
Number of Options, Granted	0