Number of Independent Trustees

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- Definition

Number of Tranches

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No definition available.

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- Definition

Represents the number of trustees to whom common shares granted during the period.

+ References

No definition available.

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- Definition

Represents the aggregate market value at grant date for vested equity-based awards during the period on other than stock (or unit) options plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

No definition available.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Vesting as a Percentage of Granted

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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.

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Face amount or stated value per share of common stock.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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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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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

Percentage of vesting of share-based compensation awards.

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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).

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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).

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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.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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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.

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- Definition

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

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- Definition

Price of a single share of a number of saleable stocks of a company.

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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.

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Share-Based Compensation - Narrative (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 28, 2014 trustee	Jan. 28, 2014 trustee	Mar. 25, 2014	Dec. 31, 2011	Jul. 09, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Par value (in dollars per share)	$ 0.01	$ 0.01
Number of shares granted under the Award Plan (in shares)	4,000	83,450	83,617
Granted shares value (in dollars per share)	$ 23.46	$ 23.29	$ 15.99
Unvested restricted shares (in shares)	0	130,914	114,703				103,615
Shares vested (in shares)	134,914	66,639	71,244
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of independent trustees receiving pro-rata grant of fully vested common shares				5
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)	713,727
Vesting period	4 years
Granted shares value (in dollars per share)	$ 26.66			26.66
Unvested restricted shares (in shares)	710,182	0
Shares vested (in shares)	3,545
Estimated future compensation expense for unvested shares	$ 17.4
Weighted average period over which compensation expense will be recorded	3 years 6 months
Restricted shares \| Vesting in 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	86,517
Restricted shares \| Vesting in 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	155,916
Restricted shares \| Vesting in 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	155,916
Restricted shares \| Vesting in 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	311,833
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)	1,266,237
Granted shares value (in dollars per share)	$ 15.99
Unvested restricted shares (in shares)	1,266,237	0
Shares vested (in shares)	0
Estimated future compensation expense for unvested shares	19.2
Weighted average period over which compensation expense will be recorded	3 years 3 months 18 days
Number of tranches	2
Restricted stock units \| Vesting on October 28, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent	50.00%
Restricted stock units \| Vesting on October 28, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent	50.00%
Share award plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	3.4	1.8	1.2
Common shares available for issuance (in shares)	849,569
Trustees \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares granted in period (in shares)					2,000
Par value (in dollars per share)					$ 0.01
Share price (in dollars per share)					$ 23.46
Number of trustees					2
Trustees \| Share award plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)		2,000	2,000
Aggregate market value of shares awarded		0.2	0.2
RMR \| Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)		73,450	71,617
Vesting period	4 years
Employee Stock \| RMR \| Officers and Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	3.4
Employee Stock \| RMR \| Officers and Employees \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares issued (in shares)						130,914
SIR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price (in dollars per share)								$ 32.04
Compensation expense		0.4	0.5
Minimum \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of RSU grants grant recipients may earn				0.00%
Maximum \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of RSU grants grant recipients may earn				100.00%
General and Administrative Expense \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 2.6