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Represents the information about grant price on the last trading day.

+ References

No definition available.

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- Definition

Represents the number of share options reclassified as grants to employees.

+ References

No definition available.

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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

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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- 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

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

-Publisher FASB

-Name Accounting Standards Codification

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-Paragraph 2

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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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- Definition

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

+ References

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- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

+ 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)(1)(iii)

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- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ 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)(1)(iii)

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- Definition

Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ 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 (d)(2)

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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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-Subparagraph (c)(1)(iv)(3)

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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-Subparagraph (c)(1)(iv)(1)

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- Definition

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

+ References

No definition available.

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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

+ References

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- Definition

Number of options outstanding, including both vested and non-vested options.

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

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Weighted average remaining contractual term for option awards outstanding, 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

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-Name Accounting Standards Codification

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-Paragraph 2

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

+ References

No definition available.

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- Definition

Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

+ References

No definition available.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

No definition available.

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- Definition

Number of share options (or share units) exercised during the current period.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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-Name Accounting Standards Codification

-Topic 505

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-Name Regulation S-X (SX)

-Number 210

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-Article 5

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Shareholders' equity (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	12 Months Ended			36 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Jun. 10, 2013	Apr. 30, 2013
Aggregate intrinsic value
Intrinsic value for activities other than exercises	$ 17.03
2012 Equity Incentive Plan \| Board of Trustees
Class of Stock
Vesting period		4 years	4 years	4 years
Expiration period					10 years
2012 Equity Incentive Plan \| Stock options
Stock Options
Outstanding at beginning of the period (in shares)		1,190,000	700,000
Granted (in shares)		1,270,000	550,000	700,000
Exercised (in shares)		(28,750)
Forfeited (in shares)		(266,250)	(60,000)
Outstanding at end of the period (in shares)	2,165,000	2,165,000	1,190,000	700,000	2,165,000
Exercisable at end of the period (in shares)	375,000	375,000			375,000
Weighted Average Exercise Price
Outstanding at beginning of the period (in dollars per share)		15.48	15.00
Granted (in dollars per share)		16.74	16.03	15.00
Exercised (in dollars per share)		15.00
Forfeited (in dollars per share)		15.88	15.00
Outstanding at end of the period (in dollars per share)	$ 16.17	16.17	15.48	15.00	16.17
Exercisable at end of the period (in dollars per share)	$ 15.31	15.31			15.31
Aggregate intrinsic value
Weighted average remaining life (years)		8 years 9 months 18 days	9 years 3 months 18 days	9 years 10 months 24 days
Weighted average exercisable (years)		8 years 2 months 12 days
Aggregate intrinsic value	$ 1,890	1,890	862		1,890
Aggregate intrinsic value exercised		74
Aggregate intrinsic value exercisable	$ 645	645			645
2012 Equity Incentive Plan \| Restricted stock units
Class of Stock
Stock options granted		92,000
2012 Equity Incentive Plan \| Class A common shares
Class of Stock
Shares available for issuance				1,500,000			6,000,000
2012 Equity Incentive Plan \| Class A common shares \| Board of Trustees
Class of Stock
Stock options granted				50,000
2012 Equity Incentive Plan \| Class A common shares \| Stock options
Class of Stock
Stock options granted		1,270,000	550,000
2012 Equity Incentive Plan \| Class A common shares \| Stock options \| Sponsor
Class of Stock
Stock options granted				650,000
Options reclassified as grants to employees						485,000