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Equity Incentive Plan - Additional Information (Details) $ / shares in Units, $ in Millions |  |  |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Jan. 16, 2019 shares | Mar. 01, 2018 $ / shares shares | Jun. 01, 2015 shares | May 17, 2013 shares | Jan. 31, 2018 shares | Jan. 31, 2017 shares | Jan. 31, 2016 shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) shares
Independent Trustees |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Trustee fees | $ |  |  |  |  |  |  |  | $ 0.1 | $ 0.1 | $ 0.1
Common shares issued as compensation for services performed (in shares) |  |  |  |  | 21,670 | 23,980 | 26,488 |  |  |
Independent Trustees | Subsequent Event |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Common shares issued as compensation for services performed (in shares) | 27,870 |  |  |  |  |  |  |  |  |
Minimum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Trustee fees paid in shares (up to 100%) (at least 50%) (in percentage) |  |  |  |  |  |  |  | 50.00% |  |
Maximum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Trustee fees paid in shares (up to 100%) (at least 50%) (in percentage) |  |  |  |  |  |  |  | 100.00% |  |
2018 Time-Based LTIP Unit Award |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of Shares, Granted (in shares) |  | 97,968 |  |  |  |  |  |  |  |
Shares granted (in shares) |  | 97,968 |  |  |  |  |  |  |  |
Equity Incentive Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares authorized (in shares) |  |  |  | 3,000,000 |  |  |  |  |  |
Equity Incentive Plan | Minimum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period for share awards under equity |  |  |  | 3 years |  |  |  |  |  |
Equity Incentive Plan | Maximum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period for share awards under equity |  |  |  | 5 years |  |  |  |  |  |
2010 Equity Incentive Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Common shares available for issuance (in shares) |  |  |  |  |  |  |  | 1,400,529 |  |
Number of trading days preceding the reporting date for which average of closing price of common shares is taken |  |  |  |  |  |  |  | 10 days |  |
Restricted Stock |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of Shares, Granted (in shares) |  |  |  |  |  |  |  | 5,000 | 5,000 | 0
Unrecognized compensation costs | $ |  |  |  |  |  |  |  | $ 0.1 | $ 0.1 |
Weighted - average period for recognition of unrecognized compensation costs |  |  |  |  |  |  |  | 2 years 4 months 24 days |  |
Compensation expense recognized | $ |  |  |  |  |  |  |  | $ 0.1 | $ 0.8 | $ 1.3
Shares granted (in shares) |  |  |  |  |  |  |  | 5,000 | 5,000 | 0
Shares forfeited (in shares) |  |  |  |  |  |  |  | 24,096 | 25,870 | 0
Long Term Incentive Plan Units |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of Shares, Granted (in shares) |  |  | 183,300 |  |  |  |  | 244,917 | 223,922 | 112,251
Weighted - average period for recognition of unrecognized compensation costs |  |  |  |  |  |  |  | 1 year 9 months 18 days |  |
Compensation expense recognized | $ |  |  |  |  |  |  |  | $ 3.6 | $ 2.5 | $ 1.2
Exchange ratio |  |  |  |  |  |  |  | 1 |  |
Shares granted (in shares) |  |  | 183,300 |  |  |  |  | 244,917 | 223,922 | 112,251
Shares forfeited (in shares) |  |  |  |  |  |  |  | 183,300 | 0 | 0
Percent of units with full parity that have vested |  |  |  |  |  |  |  | 100.00% |  |
Total unrecognized compensation cost related to LTIP Units | $ |  |  |  |  |  |  |  | $ 5.0 | $ 4.4 |
Long Term Incentive Plan Units | Awarded June 1, 2015 |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of Shares, Granted (in shares) |  |  | 183,300 |  |  |  |  |  |  |
Shares granted (in shares) |  |  | 183,300 |  |  |  |  |  |  |
2018 Performance-Based LTIP Unit Awards |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of Shares, Granted (in shares) |  | 146,949 |  |  |  |  |  |  |  |
Shares granted (in shares) |  | 146,949 |  |  |  |  |  |  |  |
Grants in period, intrinsic value, amount (in dollars per share) | $ / shares |  | $ 17.02 |  |  |  |  |  |  |  |
2018 Performance-Based LTIP Unit Awards | Minimum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Percentage of target value to be paid out |  |  |  |  |  |  |  | 50.00% |  |
2018 Performance-Based LTIP Unit Awards | Maximum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Percentage of target value to be paid out |  |  |  |  |  |  |  | 150.00% |  |

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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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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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). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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- Definition Per share weighted average intrinsic value of equity-based compensation awards granted. Excludes stock and unit options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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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). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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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 No definition available. + Details
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