Office Properties Income Trust (OPI) 10-Q 3 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 30, 2019
Document and Entity Information
Entity Registrant Name	Office Properties Income Trust
Entity Central Index Key	0001456772
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		48,090,108
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Real estate properties:
Land	$ 918,992	$ 924,164
Buildings and improvements	3,001,385	3,020,472
Total real estate properties, gross	3,920,377	3,944,636
Accumulated depreciation	(386,688)	(375,147)
Total real estate properties, net	3,533,689	3,569,489
Assets of properties held for sale	23,999	253,501
Investment in unconsolidated joint ventures	42,505	43,665
Acquired real estate leases, net	1,000,960	1,056,558
Cash and cash equivalents	20,153	35,349
Restricted cash	4,464	3,594
Rents receivable, net	67,776	72,051
Deferred leasing costs, net	30,788	25,672
Other assets, net	202,864	178,704
Total assets	4,927,198	5,238,583
LIABILITIES AND SHAREHOLDERS’ EQUITY
Unsecured revolving credit facility	80,000	175,000
Unsecured term loans, net	234,674	387,152
Senior unsecured notes, net	2,360,063	2,357,497
Mortgage notes payable, net	326,202	335,241
Liabilities of properties held for sale	178	4,271
Accounts payable and other liabilities	114,613	145,536
Due to related persons	5,626	34,887
Assumed real estate lease obligations, net	18,838	20,031
Total liabilities	3,140,194	3,459,615
Commitments and contingencies
Shareholders’ equity:
Common shares of beneficial interest, $.01 par value: 200,000,000 shares authorized, 48,091,903 and 48,082,903 shares issued and outstanding, respectively	481	481
Additional paid in capital	2,610,666	2,609,801
Cumulative net income	180,901	146,882
Cumulative other comprehensive income (loss)	(297)	106
Cumulative common distributions	(1,004,747)	(978,302)
Total shareholders’ equity	1,787,004	1,778,968
Total liabilities and shareholders’ equity	$ 4,927,198	$ 5,238,583

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares of beneficial interest, shares authorized (in shares)	200,000,000	200,000,000
Common shares of beneficial interest, shares issued (in shares)	48,091,903	48,082,903
Common shares of beneficial interest, shares outstanding (in shares)	48,091,903	48,082,903

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Rental income	$ 174,777	$ 108,717
Expenses:
Real estate taxes	18,392	12,964
Utility expenses	9,381	6,690
Other operating expenses	30,136	22,837
Depreciation and amortization	77,521	44,204
Loss on impairment of real estate	3,204	6,116
Acquisition and transaction related costs	584	0
General and administrative	8,723	9,606
Total expenses	147,941	102,417
Gain on sale of real estate	22,092	0
Dividend income	980	304
Unrealized gain on equity securities	22,128	12,931
Interest income	248	116
Interest expense (including net amortization of debt premiums and discounts and debt issuance costs of $2,841 and $965, respectively)	(37,133)	(22,766)
Loss on early extinguishment of debt	(414)	0
Income before income tax expense and equity in earnings of an investee	34,737	(3,115)
Income tax expense	(483)	(32)
Equity in net losses of investees	(235)	(577)
Income (loss) from continuing operations	34,019	(3,724)
Income from discontinued operations	0	10,289
Net income	34,019	6,565
Other comprehensive loss:
Unrealized loss on financial instrument	(98)	0
Equity in unrealized gain (loss) of investees	66	(41)
Other comprehensive loss	(32)	(41)
Comprehensive income	33,987	6,524
Net income	34,019	6,565
Comprehensive income	0	(278)
Net income (loss) available for common shareholders	$ 34,019	$ 6,287
Weighted average common shares outstanding (basic) (in shares)	48,031	24,760
Weighted average common shares outstanding (diluted) (in shares)	48,046	24,760
Income from discontinued operations
Income (loss) from continuing operations (basic and diluted) (in dollars per share)	$ 0.71	$ (0.16)
Income from discontinued operations (in dollars per share)	0	0.42
Net income available for common shareholders (basic and diluted) (in dollars per share)	$ 0.71	$ 0.25

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net amortization of debt premiums and discounts and deferred financing fees	$ 2,841	$ 965

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 34,019	$ 6,565
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	23,629	17,172
Net amortization of debt premiums, discounts and issuance costs	2,841	965
Gain on sale of real estate	(22,092)	0
Loss on early extinguishment of debt	414	0
Straight line rental income	(6,794)	(3,091)
Amortization of acquired real estate leases	53,837	26,790
Amortization of deferred leasing costs	1,350	1,120
Other non-cash expenses, net	593	(334)
Loss on impairment of real estate	3,204	6,116
Unrealized gain on equity securities	(22,128)	(12,931)
Equity in net losses of investees	235	577
Equity in earnings of Select Income REIT included in discontinued operations	0	(10,289)
Distributions of earnings from Select Income REIT	0	10,289
Change in assets and liabilities:
Deferred leasing costs	(7,985)	(2,091)
Rents receivable	14,390	(1,893)
Other assets	2,873	2,296
Accounts payable and other liabilities	(30,387)	(9,679)
Due to related persons	(29,257)	3,685
Net cash provided by operating activities	18,742	35,267
CASH FLOWS FROM INVESTING ACTIVITIES:
Real estate improvements	(12,969)	(11,020)
Distributions in excess of earnings from Select Income REIT	0	2,419
Distributions in excess of earnings from unconsolidated joint ventures	521	823
Proceeds from sale of properties, net	262,779	18,797
Net cash provided by investing activities	250,331	11,019
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayment of mortgage notes payable	(8,954)	(899)
Repayment of unsecured term loans	(153,000)	0
Borrowings on unsecured revolving credit facility	85,000	25,000
Repayments on unsecured revolving credit facility	(180,000)	(25,000)
Repurchase of common shares	0	(11)
Preferred units of limited partnership distributions	0	(278)
Distributions to common shareholders	(26,445)	(42,632)
Net cash used in financing activities	(283,399)	(43,820)
Increase (decrease) in cash, cash equivalents and restricted cash	(14,326)	2,466
Cash, cash equivalents and restricted cash at beginning of period	38,943	19,680
Cash, cash equivalents and restricted cash at end of period	$ 24,617	$ 22,146

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Shares	Additional Paid In Capital	Cumulative Net Income	Cumulative Other Comprehensive Income (Loss)	Cumulative Common Distributions
Increase (Decrease) in Shareholders' Equity
Adjusted balance	$ 1,330,755	$ 248	$ 1,968,960	$ 169,137	$ 146	$ (807,736)
Balance beginning at Dec. 31, 2017	1,330,043	$ 248	1,968,960	108,144	60,427	(807,736)
Balance (in shares) at Dec. 31, 2017		24,786,479
Increase (Decrease) in Shareholders' Equity
Net current period other comprehensive loss	(41)				(41)
Shares forfeitures or repurchases	(11)		(11)
Shares forfeitures or repurchases (in shares)		(153)
Net income (loss) available for common shareholders	6,287			6,287
Distributions to common shareholders	(42,632)					(42,632)
Balance ending at Mar. 31, 2018	1,294,358	$ 248	1,968,949	175,424	105	(850,368)
Balance (in shares) at Mar. 31, 2018		24,786,326
Balance beginning at Dec. 31, 2018	1,778,968	$ 481	2,609,801	146,882	106	(978,302)
Balance (in shares) at Dec. 31, 2018		48,082,903
Increase (Decrease) in Shareholders' Equity
Share grants	865		865
Amounts reclassified from cumulative other comprehensive income to net income	(371)
Net current period other comprehensive loss	(32)				(32)
Share grants (in shares)		9,000
Net income (loss) available for common shareholders	34,019			34,019
Distributions to common shareholders	(26,445)					(26,445)
Balance ending at Mar. 31, 2019	$ 1,787,004	$ 481	$ 2,610,666	$ 180,901	$ (297)	$ (1,004,747)
Balance (in shares) at Mar. 31, 2019		48,091,903

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - Supplemental Cash Flow - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental cash flow information
Interest paid	$ 49,545	$ 27,733
Income taxes paid	7	0
Supplemental disclosure of cash and cash equivalents and restricted cash
Cash and cash equivalents	20,153	17,380
Restricted cash	4,464	4,766
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$ 24,617	$ 22,146

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements of Office Properties Income Trust and its subsidiaries, or the Company, OPI, we, us or our, are unaudited. Certain information and disclosures required by U.S. generally accepted accounting principles, or GAAP, for complete financial statements have been condensed or omitted. We believe the disclosures made are adequate to make the information presented not misleading. However, the accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes contained in our Annual Report on Form 10-K for the year ended December 31, 2018 , or our 2018 Annual Report. In the opinion of management, all adjustments, consisting of normal recurring accruals considered necessary for a fair statement of results for the interim period have been included. All intercompany transactions and balances with or among our consolidated subsidiaries have been eliminated. Our operating results for interim periods are not necessarily indicative of the results that may be expected for the full year. Reclassifications have been made to the prior years' condensed consolidated financial statements to conform to the current year’s presentation. The preparation of these financial statements in conformity with GAAP requires us to make estimates and assumptions that affect reported amounts. Actual results could differ from those estimates. Significant estimates in the condensed consolidated financial statements include purchase price allocations, useful lives of fixed assets, assessment of impairment of real estate and equity method investments and the valuation of intangible assets.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2016-02, Leases . In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements . In December 2018, the FASB issued ASU No. 2018-20 Leases (Topic 842), Narrow-Scope Improvements for Lessors . Collectively, these standards set out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). ASU No. 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight line basis over the term of the lease. ASU No. 2016-02 requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales type leases, direct financing leases and operating leases. These standards were effective as of January 1, 2019. Upon adoption, we applied the package of practical expedients that has allowed us to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classification for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. Furthermore, we applied the optional transition method in ASU No. 2018-11, which has allowed us to initially apply the new leases standard at the adoption date and recognize a cumulative effect adjustment to the opening balance of retained earnings in the adoption period, although we did not have an adjustment. Additionally, our leases met the criteria in ASU No. 2018-11 to not separate non-lease components from the related lease component; therefore, the accounting for these leases remained largely unchanged from the previous standard. The adoption of ASU No. 2016-02 and the related improvements did not have a material impact in our condensed consolidated financial statements. Upon adoption, (i) allowances for bad debts are now recognized as a direct reduction of rental income, and (ii) legal costs associated with the execution of our leases, which were previously capitalized and amortized over the life of their respective leases, are expensed as incurred. Subsequent to January 1, 2019, provisions for credit losses are now included in "rental income" in our condensed consolidated financial statements. Provisions for credit losses prior to January 1, 2019 were previously included in other operating expenses in our condensed consolidated financial statements and prior periods are not reclassified to conform to the current presentation. Revenue Recognition. We are a lessor of commercial office properties. Our leases provide our tenants with the contractual right to use and economically benefit from all of the physical space specified in the leases, therefore we have determined to evaluate our leases as lease arrangements. Our leases provide for base rent payments and in addition may include variable payments. Rental income from operating leases, including any payments derived by index or market-based indices, is recognized on a straight line basis over the lease term when we have determined that the collectability of substantially all of the lease payments is probable. Some of our leases have options to extend or terminate the lease exercisable at the option of our tenants, which are considered when determining the lease term. We do not include in our measurement of our lease receivables certain variable payments, including changes in the index or market-based indices after the inception of the lease, certain tenant reimbursements and other income until the specific events that trigger the variable payments have occurred. Such payments totaled $23,394 for the three months ended March 31, 2019. Certain of our leases contain non-lease components, such as property level operating expenses and capital expenditures reimbursed by our tenants as well as other required lease payments. We have determined that all of our leases qualify for the practical expedient to not separate the lease and non-lease components because (i) the lease components are operating leases and (ii) the timing and pattern of recognition of the non-lease components are the same as those of the lease components. We apply Accounting Standards Codification 842, Leases to the combined component. Income derived by our leases is recorded in rental income in our condensed consolidated statements of comprehensive income. Certain tenants are obligated to pay directly their obligations under their leases for insurance, real estate taxes and certain other expenses. These obligations, which have been assumed by the tenants under the terms of their respective leases, are not reflected in our condensed consolidated financial statements. To the extent any tenant responsible for any such obligations under the applicable lease defaults on such lease or if it is deemed probable that the tenant will fail to pay for such obligations, we would record a liability for such obligations. The following table presents our operating lease maturity analysis as of March 31, 2019 : Year Amount 2019 $ 409,264 2020 504,511 2021 476,943 2022 435,405 2023 390,252 Thereafter 1,286,197 Total $ 3,502,572 Right of Use Asset and Lease Liability . For leases where we are the lessee, we are required to record a right of use asset and lease liability for all leases with a term greater than 12 months. As of March 31, 2019 , we had one lease that met this criterion where we are the lessee which expires on January 31, 2021. The value of the right of use asset and related liability representing our future obligation under the lease arrangement for which we are the lessee was $3,466 as of March 31, 2019 . The right of use asset and related lease liability are included within other assets, net and accounts payable and other liabilities, respectively, within our condensed consolidated balance sheets. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires that entities use a new forward looking “expected loss” model that generally will result in the earlier recognition of allowance for credit losses. The measurement of expected credit losses is based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. ASU No. 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. We are currently assessing the potential impact the adoption of ASU No. 2016-13 will have in our condensed consolidated financial statements although lease related receivables are governed by the lease standards referred to above and are not subject to ASU No. 2016-13. We currently expect to adopt the standard using the modified retrospective approach.

Weighted Average Common Shares

Weighted Average Common Shares	3 Months Ended
	Mar. 31, 2019
Earnings Per Share, Basic and Diluted [Abstract]
Weighted Average Common Shares	Weighted Average Common Shares The following table provides a reconciliation of the weighted average number of common shares used in the calculation of basic and diluted earnings per share (in thousands): For the Three Months Ended March 31, 2019 2018 Weighted average common shares for basic earnings per share 48,031 24,760 Effect of dilutive securities: unvested share awards 15 — Weighted average common shares for diluted earnings per share (1) 48,046 24,760 (1) For the three months ended March 31, 2018, two unvested common shares were not included in the calculation of diluted earnings per share because to do so would have been antidilutive.

Real Estate Properties

Real Estate Properties	3 Months Ended
	Mar. 31, 2019
Real Estate [Abstract]
Real Estate Properties	Real Estate Properties As of March 31, 2019 , our wholly owned properties were comprised of 212 buildings with approximately 30,134,000 rentable square feet, with an aggregate undepreciated carrying value of $3,955,529 , and we had a noncontrolling ownership interest in three buildings totaling approximately 443,900 rentable square feet through two unconsolidated joint ventures in which we own 50% and 51% interests. We generally lease space at our properties on a gross lease or modified gross lease basis pursuant to fixed term contracts expiring between 2019 and 2039 . Our leases generally require us to pay all or some property operating expenses and to provide all or most property management services. During the three months ended March 31, 2019 , we entered into 32 leases for 825,475 rentable square feet, for a weighted (by rentable square feet) average lease term of 7.5 years and we made commitments for $28,804 of leasing related costs. As of March 31, 2019 , we have estimated unspent leasing related obligations of $63,580 . We regularly evaluate whether events or changes in circumstances have occurred that could indicate an impairment in the value of our long lived assets. If there is an indication that the carrying value of an asset is not recoverable, we estimate the projected undiscounted cash flows to determine if an impairment loss should be recognized. We determine the amount of any impairment loss by comparing the historical carrying value to estimated fair value. We estimate fair value through an evaluation of recent financial performance and projected discounted cash flows using standard industry valuation techniques. In addition to evaluating for impairment upon the events or changes in circumstances described above, we regularly evaluate the remaining lives of our long lived assets. If we change our estimate of the remaining lives, we allocate the carrying value of the affected assets over their revised remaining lives. Disposition Activities On February 8, 2019, we sold a property portfolio consisting of 34 buildings located in Northern Virginia and Maryland with 1,635,868 rentable square feet for $198,500 in aggregate, excluding closing costs. As of December 31, 2018, this property portfolio was included in assets held for sale and we recorded a $447 loss on impairment of real estate during the three months ended March 31, 2019 as a result of this sale. On March 18, 2019, we sold an office building located in Washington, D.C. with 129,035 rentable square feet for $70,000 , excluding closing costs. As of December 31, 2018, this building was included in assets held for sale and we recorded a $ 22,092 gain on sale of real estate during the three months ended March 31, 2019 as a result of this sale. The sales of these properties do not represent significant dispositions individually or in the aggregate nor do they represent a strategic shift. The results of operations of these properties are included in continuing operations through the date of sale in our condensed consolidated statements of comprehensive income. As of March 31, 2019 , we had two properties with an aggregate undepreciated carrying value of $35,152 classified as held for sale in our condensed consolidated balance sheet. The operating results of these two properties are included in continuing operations in our condensed consolidated statements of comprehensive income. The following table summarizes the properties held for sale as of March 31, 2019. Date of Sale Agreement Number of Office Buildings Location Square Feet Gross (1) November 2018 (2) 1 Kapolei, HI 416,956 $ 7,100 April 2019 (3) 1 Buffalo, NY 121,711 17,350 Total 2 538,667 $ 24,450 (1) Gross sale price includes purchase price adjustments, if any, and excludes closing costs. (2) Comprises of a leasable land parcel acquired from SIR in the SIR Merger (each as defined below). We expect this sale to close in the second quarter of 2019. (3) During the three months ended March 31, 2019, we recorded a $2,757 loss on impairment of real estate to reduce the carrying value of this property to its estimated fair value less costs to sell. We expect this sale to close in the second quarter of 2019. In April 2019, we entered an agreement to sell an office building located in Hanover, PA with 502,300 rentable square feet for $6,000 , excluding closing costs. This property did not meet the held for sale criteria as of March 31, 2019. This sale is expected to occur in the third quarter of 2019. In May 2019, we entered an agreement to sell an office building located in Maynard, MA with 287,037 rentable square feet for $5,000 , excluding closing costs. This property did not meet the held for sale criteria as of March 31, 2019. This sale is expected to occur in the second quarter of 2019. In addition to the properties discussed above, we are currently marketing for sale 30 office buildings, including properties acquired in the merger of Select Income REIT, or SIR, with and into our wholly owned subsidiary that closed on December 31, 2018, or the SIR Merger, comprising approximately 4.4 million square feet as of March 31, 2019 . We have determined that these properties were not impaired nor did they meet the held for sale criteria as of March 31, 2019 . We cannot be sure we will sell any of our properties that we are marketing for sale or sell them for prices in excess of our carrying values or that we will not recognize impairment losses with respect to these properties. In addition, our pending sales are subject to conditions; accordingly, we cannot be sure that we will complete these sales or that these sales will not be delayed or their terms will not change. Pro Forma Financial Information On December 31, 2018, we acquired SIR pursuant to an agreement and plan of merger that we and SIR entered into on September 14, 2018, or the Merger Agreement, as a result of which we acquired 99 buildings with approximately 16.5 million rentable square feet. The aggregate transaction value of the SIR Merger was $2,415,053 , excluding closing costs of approximately $27,497 ( $14,508 of which was paid by us and $12,989 of which was paid by SIR) and including the repayment or assumption of $1,719,772 of SIR debt. As a condition of the SIR Merger, on October 9, 2018 , we sold all of the 24,918,421 common shares of SIR we then owned, or the Secondary Sale, in an underwritten public offering at a price of $18.25 per share, raising net proceeds of $435,125 after deducting underwriting discounts and offering expenses. We used the net proceeds from the Secondary Sale to repay amounts outstanding under our revolving credit facility. In addition, as a condition of the SIR Merger, on December 27, 2018, SIR paid a pro rata distribution to SIR's shareholders of record as of the close of business on December 20, 2018 of all 45,000,000 common shares of beneficial interest of Industrial Logistics Properties Trust, or ILPT, that SIR owned, or the ILPT Distribution. For further information about these transactions, refer to our 2018 Annual Report. The following table presents our pro forma results of operations for the three months ended March 31, 2018 as if the SIR Merger, the Secondary Sale and the ILPT Distribution had occurred on January 1, 2018. The SIR results of operations included in this pro forma financial information have been adjusted to remove ILPT's results of operations for the three months ended March 31, 2018. The effect of the adjustments to remove ILPT's results of operations was to decrease pro forma rental income $40,605 for the three months ended March 31, 2018 and to decrease net income $13,312 for the three months ended March 31, 2018 from the amounts that would have otherwise been included in the pro forma results. This unaudited pro forma financial information is not necessarily indicative of what our actual results of operations would have been for the period presented or for any future period. Differences could result from numerous factors, including future changes in our portfolio of investments, capital structure, property level operating expenses and revenues, including rents expected to be received pursuant to our existing leases or leases we may enter into, changes in interest rates and other reasons. Actual future results are likely to be different from amounts presented in this unaudited pro forma financial information and such differences could be significant. Three Months Ended March 31, 2018 Rental income $ 189,446 Net income $ 9,453 Net income per common share $ 0.20 During the quarter ended March 31, 2018, we did not recognize any revenue or operating income from the assets acquired and liabilities assumed in the SIR Merger. Unconsolidated Joint Ventures We own noncontrolling interests in two joint ventures that own three buildings. We account for these investments under the equity method of accounting. As of March 31, 2019 and December 31, 2018 , our investment in unconsolidated joint ventures consisted of the following: OPI Carrying Value of Investment at Joint Venture OPI Ownership March 31, 2019 December 31, 2018 Number of Office Buildings Location Square Feet Prosperity Metro Plaza 51% $ 23,498 $ 23,969 2 Fairfax, VA 328,456 1750 H Street, NW 50% 19,007 19,696 1 Washington, D.C. 115,411 Total $ 42,505 $ 43,665 3 443,867 The following table provides a summary of the mortgage debt of our unconsolidated joint ventures: Joint Venture Interest Rate (1) Maturity Date Principal Balance at March 31, 2018 (2) Prosperity Metro Plaza 4.09% 12/1/2029 $ 50,000 1750 H Street, NW 3.69% 8/1/2024 32,000 Weighted Average / Total 3.93% $ 82,000 (1) Includes the effect of mark to market purchase accounting. (2) Reflects the entire balance of the debt secured by the properties and is not adjusted to reflect the interests in the joint venture we do not own. None of the debt is recourse to us. At March 31, 2019 , the aggregate unamortized basis difference of our unconsolidated joint ventures of $8,320 is primarily attributable to the difference between the amount we paid to purchase our interest in these joint ventures, including transaction costs, and the historical carrying value of the net assets of these joint ventures. This difference is being amortized over the remaining useful life of the properties owned by these joint ventures and the resulting amortization expense is included in equity in net losses of investees in our condensed consolidated statements of comprehensive income.

Revenue Recognition

Revenue Recognition	3 Months Ended
	Mar. 31, 2019
Revenue Recognition [Abstract]
Revenue Recognition	Revenue Recognition We recognize rental income from operating leases that contain fixed contractual rent changes on a straight line basis over the term of the lease agreements. Certain of our leases provide the tenant the right to terminate before the lease expiration date. In certain circumstances, some leases provide the tenant with the right to terminate if the legislature or other funding authority does not appropriate the funding necessary for the tenant to meet its lease obligations; we have determined the fixed non-cancelable lease term of these leases to be the full term of the lease because we believe the occurrence of early terminations to be remote contingencies based on both our historical experience and our assessments of the likelihood of lease cancellation on a separate lease basis. We increased rental income to record revenue on a straight line basis by $6,794 and $3,091 for the three months ended March 31, 2019 and 2018, respectively. Rents receivable, excluding properties classified as held for sale, include $40,640 and $34,006 of straight line rent receivables at March 31, 2019 and December 31, 2018 , respectively.

Concentration

Concentration	3 Months Ended
	Mar. 31, 2019
Risks and Uncertainties [Abstract]
Concentration	Concentration Tenant Concentration We define annualized rental income as the annualized contractual base rents from our tenants pursuant to our lease agreements as of the measurement date, plus straight line rent adjustments and estimated recurring expense reimbursements to be paid to us, and excluding lease value amortization. As of March 31, 2019, the U.S. Government, 13 state governments and three other government tenants combined were responsible for approximately 35.9% of our annualized rental income and as of March 31, 2018 the U.S. Government, 13 state governments and four other government tenants combined were responsible for approximately 63.2% of our annualized rental income. The U.S. Government is our largest tenant by annualized rental income and was responsible for approximately 25.8% and 44.0% of our annualized rental income as of March 31, 2019 and 2018 , respectively. Geographic Concentration At March 31, 2019 , our 212 wholly owned buildings were located in 38 states and the District of Columbia. Consolidated properties located in Virginia , California , Texas , the District of Columbia and Maryland were responsible for 15.1% , 11.8% , 11.6% , 9.4% and 7.1% of our annualized rental income as of March 31, 2019 , respectively. Consolidated properties located in the metropolitan Washington, D.C. market area were responsible for approximately 23.5% of our annualized rental income as of March 31, 2019 .

Indebtedness

Indebtedness	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Indebtedness	Indebtedness Our principal debt obligations at March 31, 2019 were: (1) $80,000 of outstanding borrowings under our $750,000 unsecured revolving credit facility; (2) $235,000 outstanding principal amount under our unsecured term loan; (3) $2,410,000 aggregate outstanding principal amount of senior unsecured notes; and (4) $329,309 aggregate outstanding principal amount of mortgage notes. Our $750,000 revolving credit facility and our term loan are governed by a credit agreement, or our credit agreement, with a syndicate of institutional lenders that includes a number of features common to all of these credit arrangements. Our credit agreement also includes a feature under which the maximum aggregate borrowing availability may be increased to up to $2,185,000 on a combined basis in certain circumstances. Our $750,000 revolving credit facility is available for general business purposes, including acquisitions. The maturity date of our revolving credit facility is January 31, 2023 and, subject to the payment of an extension fee and meeting other conditions, we have the option to extend the stated maturity date of our revolving credit facility by two additional six month periods. We can borrow, repay and reborrow funds available under our revolving credit facility until maturity and no principal repayment is due until maturity. We are required to pay interest at a rate of LIBOR plus a premium, which was 110 basis points per annum at March 31, 2019 , on borrowings under our revolving credit facility. We also pay a facility fee on the total amount of lending commitments under our revolving credit facility, which was 25 basis points per annum at March 31, 2019 . Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of March 31, 2019 and December 31, 2018, the annual interest rate payable on borrowings under our revolving credit facility was 3.5% and 3.6% , respectively. The weighted average annual interest rate for borrowings under our revolving credit facility was 3.5% and 2.8% for the three months ended March 31, 2019 and 2018 , respectively. As of March 31, 2019 and April 30, 2019 , we had $80,000 and $65,000 , respectively, outstanding under our revolving credit facility, and $670,000 and $685,000 , respectively, available for borrowing under our revolving credit facility. Our remaining $300,000 term loan, which matures on March 31, 2020 , is prepayable without penalty at any time. We are required to pay interest at a rate of LIBOR plus a premium, which was 140 basis points per annum at March 31, 2019 , on the amount outstanding under this term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of both March 31, 2019 and December 31, 2018, the annual interest rate for the amount outstanding under this term loan was 3.9% . The weighted average annual interest rate under this term loan was 3.9% and 3.0% for the three months ended March 31, 2019 and 2018 , respectively. On March 19, 2019, we repaid $65,000 of the principal balance without penalty using proceeds from the sale of a property leaving a principal balance remaining under this term loan of $235,000 . Our $250,000 term loan, which was scheduled to mature on March 31, 2022 and had a principal balance of $88,000 as of December 31, 2018, was repaid in full on February 11, 2019, without penalty, using proceeds from the sale of a property portfolio. The weighted average annual interest rate under this term loan was 4.3% for the period from January 1, 2019 to February 11, 2019, and 3.4% for the three months ended March 31, 2018. As a result of the principal payments of our term loans, we recognized a loss on early extinguishment of debt of $414 for the three months ended March 31, 2019 to write off a proportionate amount of unamortized debt issuance costs. Our credit agreement and senior unsecured notes indentures and their supplements provide for acceleration of payment of all amounts due thereunder upon the occurrence and continuation of certain events of default, such as, in the case of our credit agreement, a change of control of us, which includes The RMR Group LLC, or RMR LLC, ceasing to act as our business and property manager. Our credit agreement and our senior unsecured notes indentures and their supplements also contain covenants, including those that restrict our ability to incur debts, require us to maintain certain financial ratios and, in the case of our credit agreement, restrict our ability to make distributions under certain circumstances. We believe we were in compliance with the terms and conditions of the respective covenants under our credit agreement and senior unsecured notes indentures and their supplements at March 31, 2019 . On March 1, 2019, we repaid at maturity, at par plus accrued interest, a mortgage note secured by one property with an outstanding principal balance of $7,890 using cash on hand. At March 31, 2019 , eleven of our consolidated buildings with an aggregate net book value of $609,048 are encumbered by mortgage notes with an aggregate principal amount of $329,309 . Our mortgage notes are non-recourse, subject to certain limited exceptions and do not contain any material financial covenants.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	Fair Value of Assets and Liabilities The table below presents certain of our assets measured at fair value at March 31, 2019 , categorized by the level of inputs, as defined in the fair value hierarchy under GAAP, used in the valuation of each asset: Fair Value at Reporting Date Using Description Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Recurring Fair Value Measurements Assets: Investment in RMR Inc. (1) $ 170,808 $ 170,808 $ — $ — Non-Recurring Fair Value Measurements Assets: Assets of properties held for sale (2) $ 16,848 $ — $ 16,848 $ — (1) Our 2,801,061 shares of class A common stock of The RMR Group Inc., or RMR Inc., which are included in other assets in our condensed consolidated balance sheets, are reported at fair value which is based on quoted market prices (Level 1 inputs as defined in the fair value hierarchy under GAAP). Our historical cost basis for these shares is $111,117 as of March 31, 2019 . During the three months ended March 31, 2019 and 2018, we recorded an unrealized gain of $22,128 and $12,931 , respectively, to adjust our investment in RMR Inc. to its fair value. (2) We estimated the fair value of one building we have agreed to sell located in Buffalo, NY at March 31, 2019 based upon a negotiated sale agreement with a third party less estimated s ale costs (Level 2 inputs as defined in the fair value hierarchy under GAAP). See Note 4 for further details. In addition to the assets described in the table above, our financial instruments include our cash and cash equivalents, restricted cash, rents receivable, a mortgage note receivable, accounts payable, a revolving credit facility, an unsecured term loan, senior unsecured notes, mortgage notes payable, amounts due to related persons, other accrued expenses and security deposits. At March 31, 2019 and December 31, 2018, the fair values of our financial instruments approximated their carrying values in our condensed consolidated financial statements, due to their short term nature or floating interest rates, except as follows: As of March 31, 2019 As of December 31, 2018 Financial Instrument Carrying Amount (1) Fair Value Carrying Amount (1) Fair Value Senior unsecured notes, 3.75% interest rate, due in 2019 $ 349,524 $ 350,586 $ 349,239 $ 348,903 Senior unsecured notes, 3.60% interest rate, due in 2020 399,343 401,040 399,146 399,146 Senior unsecured notes, 4.00% interest rate, due in 2022 296,966 300,845 296,735 295,047 Senior unsecured notes, 4.15% interest rate, due in 2022 297,001 303,428 296,736 296,736 Senior unsecured notes, 4.25% interest rate, due in 2024 338,307 336,137 337,736 337,736 Senior unsecured notes, 4.50% interest rate, due in 2025 378,260 387,404 377,329 377,329 Senior unsecured notes, 5.875% interest rate, due in 2046 300,662 313,100 300,576 274,288 Mortgage notes payable 326,202 328,809 335,241 336,365 Total $ 2,686,265 $ 2,721,349 $ 2,692,738 $ 2,665,550 (1) Includes unamortized debt premiums, discounts and issuance costs. We estimated the fair value of our senior unsecured notes (except for our senior unsecured notes due in 2046) using an average of the bid and ask price of the notes as of the measurement date (Level 2 inputs as defined in the fair value hierarchy under GAAP). We estimated the fair value of our senior unsecured notes due 2046 based on the closing price on The Nasdaq Stock Market LLC, or Nasdaq, as of the measurement date (Level 1 inputs as defined in the fair value hierarchy under GAAP). We estimated the fair values of our mortgage notes payable by using discounted cash flow analyses and currently prevailing market rates as of the measurement date (Level 3 inputs as defined in the fair value hierarchy under GAAP). Because Level 3 inputs are unobservable, our estimated fair value may differ materially from the actual fair value.

Shareholders' Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity Share Awards On February 27, 2019, in connection with the election of three of our Trustees we granted each Trustee 3,000 of our common shares, valued at $29.95 per share, the closing price of our common shares on Nasdaq on that day. Share Purchases On April 5, 2019, we purchased 1,795 of our common shares valued at $28.96 per share, the closing price of our common shares on Nasdaq on that day, from a former officer of RMR LLC in satisfaction of tax withholding and payment obligations in connection with the vesting of awards of our common shares. Distributions On February 21, 2019 , we paid a regular quarterly distribution to common shareholders of record on January 28, 2019 of $0.55 per share, or $26,445 . On April 18, 2019 , we declared a regular quarterly distribution to common shareholders of record on April 29, 2019 of $0.55 per share, or approximately $26,450 . We expect to pay this distribution on or about May 16, 2019. Cumulative Other Comprehensive Income Cumulative other comprehensive income represents our share of the comprehensive income of Affiliates Insurance Company, an Indiana insurance company, or AIC. See Note 11 for further information regarding this investment.

Business and Property Managemen

Business and Property Management Agreements with RMR LLC	3 Months Ended
	Mar. 31, 2019
Property Management Fee [Abstract]
Business and Property Management Agreements with RMR LLC	Business and Property Management Agreements with RMR LLC We have no employees. The personnel and various services we require to operate our business are provided to us by RMR LLC. We have two agreements with RMR LLC to provide management services to us: (1) a business management agreement, which relates to our business generally; and (2) a property management agreement, which relates to our property level operations. Prior to completion of the SIR Merger, SIR had similar business and property management agreements with RMR LLC on substantially similar terms, which agreements were terminated in connection with the merger. See Notes 4 and 11 for further information regarding our relationship, agreements and transactions with SIR and RMR LLC. Pursuant to our business management agreement, we recognized net business management fees of $5,722 and $7,309 for the three months ended March 31, 2019 and 2018 , respectively. Based on our common share total return, as defined in our business management agreement, as of March 31, 2019 , no estimated 2019 incentive fees are included in the net business management fees we recognized for the three months ended March 31, 2019 . The actual amount of annual incentive fees for 2019, if any, will be based on our common share total return, as defined in our business management agreement, for the three year period ending December 31, 2019, and will be payable in 2020. The net business management fees recognized for the three months ended March 31, 2018 included $2,887 of accrued estimated business management incentive fees as of March 31, 2018. No business management incentive fee was payable for the year ended December 31, 2018. We include business management fees in general and administrative expenses in our condensed consolidated statements of comprehensive income. Pursuant to our property management agreement, we recognized aggregate net property management and construction supervision fees of $5,449 and $3,349 for the three months ended March 31, 2019 and 2018 , respectively. These amounts are included in other operating expenses or have been capitalized, as appropriate, in our condensed consolidated financial statements. In addition, we paid RMR LLC $2,185 in January 2019 for SIR’s 2018 business management, property management and construction supervision fees that it had accrued, but not paid, as of December 31, 2018. We also paid RMR LLC a business management incentive fee of $25,817 , which represented the incentive fee incurred, but not paid, by SIR for the year ended December 31, 2018. We had assumed the obligation to pay these amounts as a result of the SIR Merger. We are generally responsible for all our operating expenses, including certain expenses incurred or arranged by RMR LLC on our behalf. We are generally not responsible for payment of RMR LLC’s employment, office or administrative expenses incurred to provide management services to us, except for the employment and related expenses of RMR LLC’s employees assigned to work exclusively or partly at our properties, our share of the wages, benefits and other related costs of RMR LLC's centralized accounting personnel, our share of RMR LLC’s costs for providing our internal audit function, or as otherwise agreed. Our property level operating expenses are generally incorporated into the rents charged to our tenants, including certain payroll and related costs incurred by RMR LLC. We reimbursed RMR LLC $6,553 and $4,969 for these expenses and costs for the three months ended March 31, 2019 and 2018 , respectively. We included these amounts in other operating expenses and general and administrative expenses, as applicable, in our condensed consolidated statements of comprehensive income.

Related Person Transactions

Related Person Transactions	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
Related Person Transactions	Related Person Transactions We have relationships and historical and continuing transactions with SIR (prior to the Merger), RMR LLC, RMR Inc., AIC and others related to them, including other companies to which RMR LLC or its subsidiaries provide management services and some of which have trustees, directors or officers who are also our Trustees or officers. Our Manager, RMR LLC. We have two agreements with RMR LLC to provide management services to us. See Note 10 for further information regarding our management agreements with RMR LLC. Leases with RMR LLC. We lease office space to RMR LLC in certain of our properties for RMR LLC's property management offices. Pursuant to our lease agreements with RMR LLC, we recognized rental income from RMR LLC for leased office space of $279 and $218 for the three months ended March 31, 2019 and 2018, respectively. RMR Inc. RMR LLC is a majority owned subsidiary of RMR Inc. and RMR Inc. is the managing member of RMR LLC. Adam D. Portnoy, one of our Managing Trustees, is the sole trustee, an officer and the controlling shareholder of ABP Trust, which is the controlling shareholder of RMR Inc., a managing director, president and chief executive officer of RMR Inc. and an officer and employee of RMR LLC. David M. Blackman, our other Managing Trustee and our President and Chief Executive Officer, also serves as an executive officer of RMR LLC, and each of our other officers is an officer and employee of RMR LLC. As of March 31, 2019 , we owned 2,801,061 shares of class A common stock of RMR Inc. See Note 8 for further information regarding our investment in RMR Inc. SIR . As described further in Note 4, we completed the SIR Merger effective December 31, 2018. Our Managing Trustees and one of our Independent Trustees previously served as managing trustees and independent trustees, respectively, of SIR, our President and Chief Executive Officer also served as SIR’s president and chief executive officer, Jeffrey C. Leer, our Chief Financial Officer and Treasurer, served as SIR’s chief financial officer and treasurer and each of SIR’s officers was also an officer and employee of RMR LLC. RMR LLC provides management services to us and provided management services to SIR until it ceased to exist. See Note 4 for further information regarding the Merger and our previous investment in SIR. AIC . We, ABP Trust and five other companies to which RMR LLC provides management services currently own AIC in equal amounts. We and the other AIC shareholders participate in a combined property insurance program arranged and insured or reinsured in part by AIC. As of March 31, 2019 and December 31, 2018, our investment in AIC had a carrying value of $9,221 and $8,751 , respectively. These amounts are included in other assets in our condensed consolidated balance sheets. We recognized income of $404 and $44 for the three months ended March 31, 2019 and 2018, respectively, which are presented as equity in net losses of investees in our condensed consolidated statements of comprehensive income. Our other comprehensive loss includes our proportionate part of unrealized gains (losses) on fixed income securities, which are owned by AIC, related to our investment in AIC. For further information about these and other such relationships and certain other related person transactions, refer to our 2018 Annual Report.

Discontinued Operations

Discontinued Operations	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations We previously accounted for our investment in SIR under the equity method and had previously reported our investment in SIR as a reportable segment. As a result of the Secondary Sale and the elimination of a reportable segment, our equity method investment in SIR is classified as discontinued operations in our condensed consolidated financial statements. See Note 4 for further information regarding the Secondary Sale. For the three months ended March 31, 2018, we recorded $10,289 of equity in earnings of SIR which is included in income from discontinued operations in our condensed consolidated statement of comprehensive income. The following presents a summarized income statement of SIR as reported in SIR’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, or the SIR Quarterly Report. References in our condensed consolidated financial statements to the SIR Quarterly Report are included as references to the source of the data only, and the information in the SIR Quarterly Report is not incorporated by reference into our condensed consolidated financial statements. Three Months Ended March 31, 2018 Rental income $ 99,755 Tenant reimbursements and other income 20,874 Total revenues 120,629 Real estate taxes 11,788 Other operating expenses 15,282 Depreciation and amortization 34,946 General and administrative 13,941 Total expenses 75,957 Dividend income 397 Unrealized gain on equity securities 16,900 Interest income 510 Interest expense (23,492 ) Loss on early extinguishment of debt (1,192 ) Income before income tax expense and equity in earnings of an investee 37,795 Income tax expense (160 ) Equity in earnings of an investee 44 Net income 37,679 Net income allocated to noncontrolling interest (4,479 ) Net income attributed to SIR $ 33,200 Weighted average common shares outstanding (basic) 89,382 Weighted average common shares outstanding (diluted) 89,390 Net income attributed to SIR per common share (basic and diluted) $ 0.37

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2016-02, Leases . In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements . In December 2018, the FASB issued ASU No. 2018-20 Leases (Topic 842), Narrow-Scope Improvements for Lessors . Collectively, these standards set out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). ASU No. 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight line basis over the term of the lease. ASU No. 2016-02 requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales type leases, direct financing leases and operating leases. These standards were effective as of January 1, 2019. Upon adoption, we applied the package of practical expedients that has allowed us to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classification for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. Furthermore, we applied the optional transition method in ASU No. 2018-11, which has allowed us to initially apply the new leases standard at the adoption date and recognize a cumulative effect adjustment to the opening balance of retained earnings in the adoption period, although we did not have an adjustment. Additionally, our leases met the criteria in ASU No. 2018-11 to not separate non-lease components from the related lease component; therefore, the accounting for these leases remained largely unchanged from the previous standard. The adoption of ASU No. 2016-02 and the related improvements did not have a material impact in our condensed consolidated financial statements. Upon adoption, (i) allowances for bad debts are now recognized as a direct reduction of rental income, and (ii) legal costs associated with the execution of our leases, which were previously capitalized and amortized over the life of their respective leases, are expensed as incurred. Subsequent to January 1, 2019, provisions for credit losses are now included in "rental income" in our condensed consolidated financial statements. Provisions for credit losses prior to January 1, 2019 were previously included in other operating expenses in our condensed consolidated financial statements and prior periods are not reclassified to conform to the current presentation. Revenue Recognition. We are a lessor of commercial office properties. Our leases provide our tenants with the contractual right to use and economically benefit from all of the physical space specified in the leases, therefore we have determined to evaluate our leases as lease arrangements. Our leases provide for base rent payments and in addition may include variable payments. Rental income from operating leases, including any payments derived by index or market-based indices, is recognized on a straight line basis over the lease term when we have determined that the collectability of substantially all of the lease payments is probable. Some of our leases have options to extend or terminate the lease exercisable at the option of our tenants, which are considered when determining the lease term. We do not include in our measurement of our lease receivables certain variable payments, including changes in the index or market-based indices after the inception of the lease, certain tenant reimbursements and other income until the specific events that trigger the variable payments have occurred. Such payments totaled $23,394 for the three months ended March 31, 2019. Certain of our leases contain non-lease components, such as property level operating expenses and capital expenditures reimbursed by our tenants as well as other required lease payments. We have determined that all of our leases qualify for the practical expedient to not separate the lease and non-lease components because (i) the lease components are operating leases and (ii) the timing and pattern of recognition of the non-lease components are the same as those of the lease components. We apply Accounting Standards Codification 842, Leases to the combined component. Income derived by our leases is recorded in rental income in our condensed consolidated statements of comprehensive income. Certain tenants are obligated to pay directly their obligations under their leases for insurance, real estate taxes and certain other expenses. These obligations, which have been assumed by the tenants under the terms of their respective leases, are not reflected in our condensed consolidated financial statements. To the extent any tenant responsible for any such obligations under the applicable lease defaults on such lease or if it is deemed probable that the tenant will fail to pay for such obligations, we would record a liability for such obligations. The following table presents our operating lease maturity analysis as of March 31, 2019 : Year Amount 2019 $ 409,264 2020 504,511 2021 476,943 2022 435,405 2023 390,252 Thereafter 1,286,197 Total $ 3,502,572 Right of Use Asset and Lease Liability . For leases where we are the lessee, we are required to record a right of use asset and lease liability for all leases with a term greater than 12 months. As of March 31, 2019 , we had one lease that met this criterion where we are the lessee which expires on January 31, 2021. The value of the right of use asset and related liability representing our future obligation under the lease arrangement for which we are the lessee was $3,466 as of March 31, 2019 . The right of use asset and related lease liability are included within other assets, net and accounts payable and other liabilities, respectively, within our condensed consolidated balance sheets. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires that entities use a new forward looking “expected loss” model that generally will result in the earlier recognition of allowance for credit losses. The measurement of expected credit losses is based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. ASU No. 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. We are currently assessing the potential impact the adoption of ASU No. 2016-13 will have in our condensed consolidated financial statements although lease related receivables are governed by the lease standards referred to above and are not subject to ASU No. 2016-13. We currently expect to adopt the standard using the modified retrospective approach.

Recent Accounting Pronounceme_3

Recent Accounting Pronouncements (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Maturity of payments to be received	The following table presents our operating lease maturity analysis as of March 31, 2019 : Year Amount 2019 $ 409,264 2020 504,511 2021 476,943 2022 435,405 2023 390,252 Thereafter 1,286,197 Total $ 3,502,572

Weighted Average Common Shares

Weighted Average Common Shares (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share, Basic and Diluted [Abstract]
Weighted Average Common Share Amounts	The following table provides a reconciliation of the weighted average number of common shares used in the calculation of basic and diluted earnings per share (in thousands): For the Three Months Ended March 31, 2019 2018 Weighted average common shares for basic earnings per share 48,031 24,760 Effect of dilutive securities: unvested share awards 15 — Weighted average common shares for diluted earnings per share (1) 48,046 24,760 (1) For the three months ended March 31, 2018, two unvested common shares were not included in the calculation of diluted earnings per share because to do so would have been antidilutive.

Real Estate Properties (Tables)

Real Estate Properties (Tables)	3 Months Ended
	Mar. 31, 2019
Real Estate [Abstract]
Disclosure of Assets held-for-sale	The following table summarizes the properties held for sale as of March 31, 2019. Date of Sale Agreement Number of Office Buildings Location Square Feet Gross (1) November 2018 (2) 1 Kapolei, HI 416,956 $ 7,100 April 2019 (3) 1 Buffalo, NY 121,711 17,350 Total 2 538,667 $ 24,450 (1) Gross sale price includes purchase price adjustments, if any, and excludes closing costs. (2) Comprises of a leasable land parcel acquired from SIR in the SIR Merger (each as defined below). We expect this sale to close in the second quarter of 2019. (3) During the three months ended March 31, 2019, we recorded a $2,757 loss on impairment of real estate to reduce the carrying value of this property to its estimated fair value less costs to sell. We expect this sale to close in the second quarter of 2019.
Schedule of Pro Forma Information	The following table presents our pro forma results of operations for the three months ended March 31, 2018 as if the SIR Merger, the Secondary Sale and the ILPT Distribution had occurred on January 1, 2018. The SIR results of operations included in this pro forma financial information have been adjusted to remove ILPT's results of operations for the three months ended March 31, 2018. The effect of the adjustments to remove ILPT's results of operations was to decrease pro forma rental income $40,605 for the three months ended March 31, 2018 and to decrease net income $13,312 for the three months ended March 31, 2018 from the amounts that would have otherwise been included in the pro forma results. This unaudited pro forma financial information is not necessarily indicative of what our actual results of operations would have been for the period presented or for any future period. Differences could result from numerous factors, including future changes in our portfolio of investments, capital structure, property level operating expenses and revenues, including rents expected to be received pursuant to our existing leases or leases we may enter into, changes in interest rates and other reasons. Actual future results are likely to be different from amounts presented in this unaudited pro forma financial information and such differences could be significant. Three Months Ended March 31, 2018 Rental income $ 189,446 Net income $ 9,453 Net income per common share $ 0.20
Schedule of Joint Ventures	As of March 31, 2019 and December 31, 2018 , our investment in unconsolidated joint ventures consisted of the following: OPI Carrying Value of Investment at Joint Venture OPI Ownership March 31, 2019 December 31, 2018 Number of Office Buildings Location Square Feet Prosperity Metro Plaza 51% $ 23,498 $ 23,969 2 Fairfax, VA 328,456 1750 H Street, NW 50% 19,007 19,696 1 Washington, D.C. 115,411 Total $ 42,505 $ 43,665 3 443,867 The following table provides a summary of the mortgage debt of our unconsolidated joint ventures: Joint Venture Interest Rate (1) Maturity Date Principal Balance at March 31, 2018 (2) Prosperity Metro Plaza 4.09% 12/1/2029 $ 50,000 1750 H Street, NW 3.69% 8/1/2024 32,000 Weighted Average / Total 3.93% $ 82,000 (1) Includes the effect of mark to market purchase accounting. (2) Reflects the entire balance of the debt secured by the properties and is not adjusted to reflect the interests in the joint venture we do not own. None of the debt is recourse to us.

Fair Value of Assets and Liab_2

Fair Value of Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of assets measured on a recurring and non-recurring basis at fair value, categorized by the level of inputs used in the valuation assets	The table below presents certain of our assets measured at fair value at March 31, 2019 , categorized by the level of inputs, as defined in the fair value hierarchy under GAAP, used in the valuation of each asset: Fair Value at Reporting Date Using Description Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Recurring Fair Value Measurements Assets: Investment in RMR Inc. (1) $ 170,808 $ 170,808 $ — $ — Non-Recurring Fair Value Measurements Assets: Assets of properties held for sale (2) $ 16,848 $ — $ 16,848 $ — (1) Our 2,801,061 shares of class A common stock of The RMR Group Inc., or RMR Inc., which are included in other assets in our condensed consolidated balance sheets, are reported at fair value which is based on quoted market prices (Level 1 inputs as defined in the fair value hierarchy under GAAP). Our historical cost basis for these shares is $111,117 as of March 31, 2019 . During the three months ended March 31, 2019 and 2018, we recorded an unrealized gain of $22,128 and $12,931 , respectively, to adjust our investment in RMR Inc. to its fair value. (2) We estimated the fair value of one building we have agreed to sell located in Buffalo, NY at March 31, 2019 based upon a negotiated sale agreement with a third party less estimated s ale costs (Level 2 inputs as defined in the fair value hierarchy under GAAP). See Note 4 for further details.
Schedule of fair value and carrying value of financial instruments	At March 31, 2019 and December 31, 2018, the fair values of our financial instruments approximated their carrying values in our condensed consolidated financial statements, due to their short term nature or floating interest rates, except as follows: As of March 31, 2019 As of December 31, 2018 Financial Instrument Carrying Amount (1) Fair Value Carrying Amount (1) Fair Value Senior unsecured notes, 3.75% interest rate, due in 2019 $ 349,524 $ 350,586 $ 349,239 $ 348,903 Senior unsecured notes, 3.60% interest rate, due in 2020 399,343 401,040 399,146 399,146 Senior unsecured notes, 4.00% interest rate, due in 2022 296,966 300,845 296,735 295,047 Senior unsecured notes, 4.15% interest rate, due in 2022 297,001 303,428 296,736 296,736 Senior unsecured notes, 4.25% interest rate, due in 2024 338,307 336,137 337,736 337,736 Senior unsecured notes, 4.50% interest rate, due in 2025 378,260 387,404 377,329 377,329 Senior unsecured notes, 5.875% interest rate, due in 2046 300,662 313,100 300,576 274,288 Mortgage notes payable 326,202 328,809 335,241 336,365 Total $ 2,686,265 $ 2,721,349 $ 2,692,738 $ 2,665,550 (1) Includes unamortized debt premiums, discounts and issuance costs.

Discontinued Operations (Tables

Discontinued Operations (Tables)	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Schedule of discontinued operations	The following presents a summarized income statement of SIR as reported in SIR’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, or the SIR Quarterly Report. References in our condensed consolidated financial statements to the SIR Quarterly Report are included as references to the source of the data only, and the information in the SIR Quarterly Report is not incorporated by reference into our condensed consolidated financial statements. Three Months Ended March 31, 2018 Rental income $ 99,755 Tenant reimbursements and other income 20,874 Total revenues 120,629 Real estate taxes 11,788 Other operating expenses 15,282 Depreciation and amortization 34,946 General and administrative 13,941 Total expenses 75,957 Dividend income 397 Unrealized gain on equity securities 16,900 Interest income 510 Interest expense (23,492 ) Loss on early extinguishment of debt (1,192 ) Income before income tax expense and equity in earnings of an investee 37,795 Income tax expense (160 ) Equity in earnings of an investee 44 Net income 37,679 Net income allocated to noncontrolling interest (4,479 ) Net income attributed to SIR $ 33,200 Weighted average common shares outstanding (basic) 89,382 Weighted average common shares outstanding (diluted) 89,390 Net income attributed to SIR per common share (basic and diluted) $ 0.37

Recent Accounting Pronounceme_4

Recent Accounting Pronouncements - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Accounting Policies [Abstract]
Variable payments excluded from measurement of lease receivable	$ 23,394
2019	409,264
2020	504,511
2021	476,943
2022	435,405
2023	390,252
Thereafter	1,286,197
Total	3,502,572
ROU asset	3,466
Operating lease liability	$ 3,466

Weighted Average Common Share_2

Weighted Average Common Shares - Weighted Average Shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share, Basic and Diluted [Abstract]
Weighted average common shares for basic earnings per share (in shares)	48,031	24,760
Effect of dilutive securities: unvested share awards (in shares)	15	0
Weighted average common shares for diluted earnings per share (in shares)	48,046	24,760
Unvested common shares (in shares)		2

Real Estate Properties - Additi

Real Estate Properties - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)ft²leasebuildingjoint_venture
Real Estate Properties [Line Items]
Number of joint ventures | joint_venture	2
Number of leases entered | lease	32
Rentable square feet (in sqft) | ft²	825,475
Weighted average lease term	7 years 6 months
Expenditures committed on leases | $	$ 28,804
Committed but unspent tenant related obligations estimated | $	$ 63,580
Continuing operations
Real Estate Properties [Line Items]
Number of buildings | building	212
Rentable area of properties (in square feet) | ft²	30,134,000
Carry value of properties | $	$ 3,955,529
Unconsolidated Joint Ventures
Real Estate Properties [Line Items]
Number of buildings | building	3
Rentable area of properties (in square feet) | ft²	443,900
Number of buildings, noncontrolling interest | building	3
Joint Venture 1
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Joint Venture 2
Real Estate Properties [Line Items]
Equity Method Investment, Ownership Percentage	51.00%

Real Estate Properties - Dispos

Real Estate Properties - Disposition Activities (Details) $ in Thousands	Mar. 18, 2019USD ($)ft²	Feb. 08, 2019USD ($)ft²building	May 31, 2019USD ($)ft²	Apr. 30, 2019USD ($)ft²	Mar. 31, 2019USD ($)building	Mar. 31, 2018USD ($)	Mar. 31, 2019USD ($)	Mar. 31, 2019ft²	Mar. 31, 2019property	Dec. 31, 2018USD ($)
Real Estate Properties [Line Items]
Net book value							$ 3,533,689			$ 3,569,489
Loss on impairment of real estate					$ 3,204	$ 6,116
Gain (loss) on sale of real estate					$ 22,092	$ 0
Assets of properties held for sale							23,999			$ 253,501
Held-for-sale
Real Estate Properties [Line Items]
Number of properties					2				2
Rentable area of properties (in square feet) | ft²								538,667
Aggregate sale price of properties sold, excluding closing costs					$ 24,450
Assets of properties held for sale							$ 35,152
Office Building | Disposal Group, Disposed of by Sale | Northern Virginia and Maryland
Real Estate Properties [Line Items]
Number of buildings | building		34
Rentable area of properties (in square feet) | ft²		1,635,868
Aggregate sale price of properties sold, excluding closing costs		$ 198,500
Loss on impairment of real estate					$ 447
Office Building | Disposal Group, Disposed of by Sale | District of Columbia
Real Estate Properties [Line Items]
Rentable area of properties (in square feet) | ft²	129,035
Aggregate sale price of properties sold, excluding closing costs	$ 70,000
Gain (loss) on sale of real estate	$ 22,092
Buildings and Properties Acquired in SIR Merger | Disposal Group, Disposed of by Sale
Real Estate Properties [Line Items]
Number of buildings | building					30
Rentable area of properties (in square feet) | ft²								4,400,000
Subsequent Event | Office Building | Disposal Group, Disposed of by Sale | Hanover, PA
Real Estate Properties [Line Items]
Rentable area of properties (in square feet) | ft²				502,300
Aggregate sale price of properties sold, excluding closing costs				$ 6,000
Forecast | Office Building | Disposal Group, Disposed of by Sale | Maynard, MA
Real Estate Properties [Line Items]
Rentable area of properties (in square feet) | ft²			287,037
Aggregate sale price of properties sold, excluding closing costs			$ 5,000

Real Estate Properties - Assets

Real Estate Properties - Assets Held-for-Sale (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)building	Mar. 31, 2018USD ($)	Mar. 31, 2019ft²	Mar. 31, 2019property
Real Estate Properties [Line Items]
Loss on impairment of real estate	$ 3,204	$ 6,116
Held-for-sale
Real Estate Properties [Line Items]
Number of Office Buildings	2			2
Square Footage (in square feet) | ft²			538,667
Gross Sale Price	$ 24,450
Held-for-sale | Kapolei, HI
Real Estate Properties [Line Items]
Number of Office Buildings | building	1
Square Footage (in square feet) | ft²			416,956
Gross Sale Price	$ 7,100
Held-for-sale | Buffalo, NY
Real Estate Properties [Line Items]
Number of Office Buildings | building	1
Square Footage (in square feet) | ft²			121,711
Gross Sale Price	$ 17,350
Loss on impairment of real estate	$ 2,757

Real Estate Properties - Merger

Real Estate Properties - Merger With Select Income REIT (Details) $ / shares in Units, $ in Thousands, ft² in Millions	Dec. 31, 2018USD ($)ft²property	Dec. 27, 2018shares	Oct. 09, 2018USD ($)$ / sharesshares
SIR
Business Acquisition [Line Items]
Number of properties acquired | property	99
Rentable area of properties (in square feet) | ft²	16.5
Consideration transferred	$ 2,415,053
Closing costs	27,497
Payments for closing costs	14,508
Debt assumed	1,719,772
SIR | SIR
Business Acquisition [Line Items]
Payments for closing costs	$ 12,989
Underwritten public offering | Common shares
Business Acquisition [Line Items]
Shares sold (in shares) | shares			24,918,421
Price per share (in dollars per share) | $ / shares			$ 18.25
Proceeds from sale of shares			$ 435,125
ILPT | SIR
Business Acquisition [Line Items]
Shares holding (in shares) | shares		45,000,000

Real Estate Properties - Pro Fo

Real Estate Properties - Pro Forma (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)$ / shares
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Rental income	$ 189,446
Net income	$ 9,453
Net income per common share (in dollars per share) | $ / shares	$ 0.20
Acquisition-related costs
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Decrease in revenues	$ 40,605
Decrease in net income	$ 13,312

Real Estate Properties - Schedu

Real Estate Properties - Schedule of Joint Ventures (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)ft²buildingjoint_venture	Dec. 31, 2018USD ($)
Real Estate [Line Items]
Number of joint ventures | joint_venture	2
Unconsolidated Joint Ventures
Real Estate [Line Items]
Investment at carrying value	$ 42,505	$ 43,665
Number of buildings | building	3
Square Feet (in square feet) | ft²	443,900
Interest rate (as a percent)	3.93%
Principal Balance	$ 82,000
Unamortized basis difference	$ 8,320
Unconsolidated Joint Ventures | Prosperity Metro Plaza
Real Estate [Line Items]
GOV Ownership	51.00%
Investment at carrying value	$ 23,498	23,969
Number of buildings | building	2
Square Feet (in square feet) | ft²	328,456
Interest rate (as a percent)	4.09%
Principal Balance	$ 50,000
Unconsolidated Joint Ventures | 1750 H Street, NW
Real Estate [Line Items]
GOV Ownership	50.00%
Investment at carrying value	$ 19,007	$ 19,696
Number of buildings | building	1
Square Feet (in square feet) | ft²	115,411
Interest rate (as a percent)	3.69%
Principal Balance	$ 32,000

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Revenue Recognition [Abstract]
Increase in rental income to record revenue on straight line basis	$ 6,794	$ 3,091
Straight line rent receivables	$ 40,640		$ 34,006

Concentration (Details)

Concentration (Details)	3 Months Ended
	Mar. 31, 2019governmentbuildinggovernment_tenantstate_governmentstate	Mar. 31, 2018government_tenantstate_government
Concentration
Number of US government | government	1
Number of state governments | state_government	13	13
Number of other governments | government_tenant	3	4
Annualized rental income, excluding properties classified as discontinued operations | Virginia
Concentration
Annualized Rental income percent	15.10%
Annualized rental income, excluding properties classified as discontinued operations | California
Concentration
Annualized Rental income percent	11.80%
Annualized rental income, excluding properties classified as discontinued operations | Texas
Concentration
Annualized Rental income percent	11.60%
Annualized rental income, excluding properties classified as discontinued operations | District of Columbia
Concentration
Concentration risk percentage	23.50%
Annualized Rental income percent	9.40%
Annualized rental income, excluding properties classified as discontinued operations | Maryland
Concentration
Annualized Rental income percent	7.10%
Annualized rental income, excluding properties classified as discontinued operations | Tenant concentration | U.S. Government, state governments and Other Four Government
Concentration
Concentration risk percentage	35.90%	63.20%
Annualized rental income, excluding properties classified as discontinued operations | Tenant concentration | U.S. Government
Concentration
Concentration risk percentage	25.80%	44.00%
Continuing operations
Concentration
Number of buildings | building	212
Number of states in which acquired properties located | state	38

Indebtedness - Debt Obligations

Indebtedness - Debt Obligations (Details) $ in Thousands	Mar. 19, 2019USD ($)	Mar. 01, 2019USD ($)	Feb. 11, 2019	Mar. 31, 2019USD ($)extension_option	Mar. 31, 2018USD ($)	Apr. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Borrowings outstanding				$ 80,000			$ 175,000
Maximum borrowing capacity on revolving credit facility				2,185,000
Aggregate principal amount on secured properties				329,309
Loss on early extinguishment of debt				414	$ 0
Unsecured term loan, due in 2020
Debt Instrument [Line Items]
Remaining borrowing capacity	$ 235,000
Maximum borrowing capacity on revolving credit facility				$ 300,000
Interest rate (as a percent)				3.8955%			3.90%
The weighted average annual interest rate (as a percent)				3.90%	3.00%
Amount of debt repaid	$ 65,000
Unsecured revolving credit facility
Debt Instrument [Line Items]
Borrowings outstanding				$ 80,000
Remaining borrowing capacity				670,000
Maximum borrowing capacity on revolving credit facility				$ 750,000
Number of extension options | extension_option				2
Extension option duration				6 months
Facility fee (as a percent)				0.25%
Interest rate (as a percent)				3.50763%			3.60%
The weighted average annual interest rate (as a percent)				3.50%	2.80%
Unsecured revolving credit facility | Subsequent Event
Debt Instrument [Line Items]
Borrowings outstanding						$ 65,000
Remaining borrowing capacity						$ 685,000
Term loans
Debt Instrument [Line Items]
Borrowings outstanding				$ 235,000
Loss on early extinguishment of debt				414
Senior unsecured notes
Debt Instrument [Line Items]
Borrowings outstanding				$ 2,410,000
LIBOR | Unsecured term loan, due in 2020
Debt Instrument [Line Items]
Interest rate premium (as a percent)				1.40%
LIBOR | Unsecured revolving credit facility
Debt Instrument [Line Items]
Interest rate premium (as a percent)				1.10%
Mortgages
Debt Instrument [Line Items]
Outstanding principal amount				$ 329,309
Amount of debt repaid		$ 7,890
Unsecured debt | Term loan due in 2022
Debt Instrument [Line Items]
Maximum borrowing capacity on revolving credit facility				$ 250,000
The weighted average annual interest rate (as a percent)			4.30%		3.40%
Long term debt							$ 88,000

Indebtedness - Additional Infor

Indebtedness - Additional Information (Details) $ in Thousands	Mar. 31, 2019USD ($)building
Debt Disclosure [Abstract]
Number of buildings secured by mortgage notes | building	11
Aggregate net book value of secured properties	$ 609,048
Aggregate principal amount on secured properties	$ 329,309

Fair Value of Assets and Liab_3

Fair Value of Assets and Liabilities - Recurring and Nonrecurring Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value of Assets and Liabilities
Common shares owned in RMR Inc. (in shares)	2,801,061
Historical cost	$ 111,117
Unrealized gain on equity securities	22,128	$ 12,931
Recurring
Fair Value of Assets and Liabilities
Investment in RMR Inc.	170,808
Recurring | Level 1 inputs
Fair Value of Assets and Liabilities
Investment in RMR Inc.	170,808
Recurring | Level 2 inputs
Fair Value of Assets and Liabilities
Investment in RMR Inc.	0
Recurring | Level 3 inputs
Fair Value of Assets and Liabilities
Investment in RMR Inc.	0
Held-for-sale | Nonrecurring
Fair Value of Assets and Liabilities
Assets of properties held for sale	16,848
Held-for-sale | Nonrecurring | Level 1 inputs
Fair Value of Assets and Liabilities
Assets of properties held for sale	0
Held-for-sale | Nonrecurring | Level 2 inputs
Fair Value of Assets and Liabilities
Assets of properties held for sale	16,848
Held-for-sale | Nonrecurring | Level 3 inputs
Fair Value of Assets and Liabilities
Assets of properties held for sale	$ 0

Fair Value of Assets and Liab_4

Fair Value of Assets and Liabilities - Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value of Financial Instruments
Senior notes	$ 2,360,063	$ 2,357,497
Mortgage notes payable, net	$ 326,202	335,241
Senior unsecured notes, 3.75% interest rate, due in 2019
Fair Value of Financial Instruments
Interest rate (as a percent)	3.75%
Senior unsecured notes, 3.60% interest rate, due in 2020
Fair Value of Financial Instruments
Interest rate (as a percent)	3.60%
Senior unsecured notes, 4.00% interest rate, due in 2022
Fair Value of Financial Instruments
Interest rate (as a percent)	4.00%
Senior unsecured notes, 4.15% interest rate, due in 2022
Fair Value of Financial Instruments
Interest rate (as a percent)	4.15%
Senior unsecured notes, 4.25% interest rate, due in 2024
Fair Value of Financial Instruments
Interest rate (as a percent)	4.25%
Senior unsecured notes, 4.50% interest rate, due in 2025
Fair Value of Financial Instruments
Interest rate (as a percent)	4.50%
Senior unsecured notes, 5.875% interest rate, due in 2046
Fair Value of Financial Instruments
Interest rate (as a percent)	5.875%
Carrying Amount
Fair Value of Financial Instruments
Mortgage notes payable, net	$ 326,202	335,241
Fair value of financial instruments	2,686,265	2,692,738
Carrying Amount | Senior unsecured notes, 3.75% interest rate, due in 2019
Fair Value of Financial Instruments
Senior notes	349,524	349,239
Carrying Amount | Senior unsecured notes, 3.60% interest rate, due in 2020
Fair Value of Financial Instruments
Senior notes	399,343	399,146
Carrying Amount | Senior unsecured notes, 4.00% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	296,966	296,735
Carrying Amount | Senior unsecured notes, 4.15% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	297,001	296,736
Carrying Amount | Senior unsecured notes, 4.25% interest rate, due in 2024
Fair Value of Financial Instruments
Senior notes	338,307	337,736
Carrying Amount | Senior unsecured notes, 4.50% interest rate, due in 2025
Fair Value of Financial Instruments
Senior notes	378,260	377,329
Carrying Amount | Senior unsecured notes, 5.875% interest rate, due in 2046
Fair Value of Financial Instruments
Senior notes	300,662	300,576
Fair Value
Fair Value of Financial Instruments
Mortgage notes payable, net	328,809	336,365
Fair value of financial instruments	2,721,349	2,665,550
Fair Value | Senior unsecured notes, 3.75% interest rate, due in 2019
Fair Value of Financial Instruments
Senior notes	350,586	348,903
Fair Value | Senior unsecured notes, 3.60% interest rate, due in 2020
Fair Value of Financial Instruments
Senior notes	401,040	399,146
Fair Value | Senior unsecured notes, 4.00% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	300,845	295,047
Fair Value | Senior unsecured notes, 4.15% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	303,428	296,736
Fair Value | Senior unsecured notes, 4.25% interest rate, due in 2024
Fair Value of Financial Instruments
Senior notes	336,137	337,736
Fair Value | Senior unsecured notes, 4.50% interest rate, due in 2025
Fair Value of Financial Instruments
Senior notes	387,404	377,329
Fair Value | Senior unsecured notes, 5.875% interest rate, due in 2046
Fair Value of Financial Instruments
Senior notes	$ 313,100	$ 274,288

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Details) $ / shares in Units, $ in Thousands	Apr. 18, 2019USD ($)$ / shares	Apr. 05, 2019$ / sharesshares	Feb. 27, 2019trustee$ / sharesshares	Feb. 21, 2019USD ($)$ / shares	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)
Share Awards
Cash distribution to common shareholders (in dollars per share)				$ 0.55
Distributions to common shareholders | $				$ 26,455	$ 26,445	$ 42,632
Subsequent Event
Share Awards
Dividends declared (in dollars per share)	$ 0.55
Dividends declared | $	$ 26,450
Common shares | Trustees
Share Awards
Shares granted (in shares) | shares			3,000
Shares granted (in dollars per share)			$ 29.95
Number of trustees | trustee			3
Former Employee of RMR LLC | Subsequent Event
Share Awards
Shares paid for tax withholding (in shares) | shares		1,795
Shares paid for tax withholding (in dollars per share)		$ 28.96

Business and Property Managem_2

Business and Property Management Agreements with RMR LLC (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2019USD ($)	Mar. 31, 2019USD ($)employeeagreement	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
RMR LLC
Related Party Transaction [Line Items]
Number of employees | employee		0
Number of agreements | agreement		2
Related party expense		$ 5,722	$ 7,309
Incentive fee			2,887
Reimbursement expense		6,553	4,969
Net Property Management and Construction Supervision Fees | RMR LLC
Related Party Transaction [Line Items]
Related party transaction amount		$ 5,449	$ 3,349
RMR LLC | Affiliated Entity
Related Party Transaction [Line Items]
Period of common share total return, incentive fees payable		3 years
SIR | Net Property Management and Construction Supervision Fees | RMR LLC
Related Party Transaction [Line Items]
Payment for incentive fees	$ 2,185			$ 25,817

Related Person Transactions (De

Related Person Transactions (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)agreementcompanyshares	Mar. 31, 2018USD ($)
Related Party Transaction [Line Items]
Equity in net losses of investees	$ (235)	$ (577)
Class A common shares
Related Party Transaction [Line Items]
Shares holding (in shares) | shares	2,801,061
RMR LLC
Related Party Transaction [Line Items]
Number of agreements | agreement	2
Revenue from related party	$ 279	218
AIC
Related Party Transaction [Line Items]
Number of entities to whom services are provided | company	5
Carrying value of equity method investments	$ 9,221	8,751
Equity in net losses of investees	$ 404	$ 44

Discontinued Operations - Addit

Discontinued Operations - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity in earnings of an investee	$ (235)	$ (577)
SIR
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity in earnings of an investee		$ 10,289

Discontinued Operations - Summa

Discontinued Operations - Summarized Income (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income	$ 174,777	$ 108,717
Real estate taxes	18,392	12,964
Other operating expenses	30,136	22,837
Depreciation and amortization	77,521	44,204
General and administrative	8,723	9,606
Total expenses	147,941	102,417
Dividend income	980	304
Unrealized gain on equity securities	22,128	12,931
Interest income	248	116
Interest expense	(37,133)	(22,766)
Loss on early extinguishment of debt	(414)	0
Income before income tax expense and equity in earnings of an investee	34,737	(3,115)
Income tax expense	(483)	(32)
Equity in earnings of an investee	(235)	(577)
Net income attributed to SIR	$ 34,019	$ 6,565
Weighted average common shares outstanding (basic) (in shares)	48,031	24,760
Weighted average common shares outstanding (diluted) (in shares)	48,046	24,760
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)	$ 0.71	$ 0.25
SIR
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity in earnings of an investee		$ 10,289
SIR | SIR
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income		99,755
Tenant reimbursements and other income		20,874
Total revenues		120,629
Real estate taxes		11,788
Other operating expenses		15,282
Depreciation and amortization		34,946
General and administrative		13,941
Total expenses		75,957
Dividend income		397
Unrealized gain on equity securities		16,900
Interest income		510
Interest expense		(23,492)
Loss on early extinguishment of debt		(1,192)
Income before income tax expense and equity in earnings of an investee		37,795
Income tax expense		(160)
Equity in earnings of an investee		44
Net income		37,679
Net income allocated to noncontrolling interest		(4,479)
Net income attributed to SIR		$ 33,200
Weighted average common shares outstanding (basic) (in shares)		89,382
Weighted average common shares outstanding (diluted) (in shares)		89,390
Net income attributed to SIR per common share (basic and diluted) (in dollars per share)		$ 0.37

Uncategorized Items - opi-20190

Label	Element	Value
Accounting Standards Update 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 712,000
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	712,000
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	60,281,000
Accounting Standards Update 2016-01 [Member] | AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (60,281,000)