Tier Reit (TIER) 10-Q 7 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Jul. 31, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	TIER REIT INC
Entity Central Index Key	1,176,373
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		50,775,348
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Real estate
Land	$ 156,517	$ 139,951
Land held for development	45,059	45,059
Buildings and improvements, net	1,160,273	1,061,418
Real estate under development	72,965	29,525
Total real estate	1,434,814	1,275,953
Cash and cash equivalents	8,359	13,800
Restricted cash	14,086	8,510
Accounts receivable, net	80,755	81,129
Prepaid expenses and other assets	17,124	28,112
Investments in unconsolidated entities	31,714	31,852
Deferred financing fees, net	3,211	1,387
Lease intangibles, net	106,058	87,047
Assets associated with real estate held for sale	0	53,348
Total assets	1,696,121	1,581,138
Liabilities
Notes payable, net	886,260	794,538
Accounts payable and accrued liabilities	82,816	81,166
Acquired below-market leases, net	25,910	17,942
Other liabilities	6,545	7,567
Obligations associated with real estate held for sale	0	2,354
Total liabilities	1,001,531	903,567
Commitments and contingencies
Equity
Preferred stock, $.0001 par value per share; 17,500,000 shares authorized at June 30, 2018, and December 31, 2017, respectively, none outstanding	0	0
Convertible stock, $.0001 par value per share; 1,000 shares authorized, none outstanding	0	0
Common stock, $.0001 par value per share; 382,499,000 shares authorized, 48,574,724 and 47,623,324 shares issued and outstanding at June 30, 2018, and December 31, 2017, respectively	5	5
Additional paid-in capital	2,632,635	2,609,540
Cumulative distributions and net loss attributable to common stockholders	(1,953,466)	(1,936,960)
Accumulated other comprehensive income	12,462	4,218
Stockholders’ equity	691,636	676,803
Noncontrolling interests	2,954	768
Total equity	694,590	677,571
Total liabilities and equity	$ 1,696,121	$ 1,581,138

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (shares)	17,500,000	17,500,000
Preferred stock, shares outstanding (shares)	0	0
Convertible stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible stock, shares authorized (shares)	1,000	1,000
Convertible stock, shares outstanding (shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (shares)	382,499,000	382,499,000
Common stock, shares issued (shares)	48,574,724	47,623,324
Common stock, shares outstanding (shares)	48,574,724	47,623,324

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Rental revenue	$ 53,990	$ 54,552	$ 108,133	$ 110,915
Expenses
Property operating expenses	12,395	13,930	25,550	28,620
Interest expense	8,369	8,235	16,478	17,015
Real estate taxes	9,074	8,753	17,828	17,313
Property management fees	97	72	182	132
General and administrative	5,377	5,626	10,880	11,333
Depreciation and amortization	27,134	22,652	51,750	47,181
Total expenses	62,446	59,268	122,668	121,594
Interest and other income	550	783	595	1,101
Loss on early extinguishment of debt	0	0	(8,988)	(545)
Loss before income taxes, equity in operations of investments, and gains (losses)	(7,906)	(3,933)	(22,928)	(10,123)
Benefit (provision) for income taxes	(214)	149	(409)	(95)
Equity in operations of investments	0	6,556	287	6,300
Income (loss) before gains (losses)	(8,120)	2,772	(23,050)	(3,918)
Gain (loss) on sale of assets	(90)	1,262	11,924	92,012
Gain (loss) on remeasurement of investment in unconsolidated entities	(152)	0	11,090	14,168
Net income (loss)	(8,362)	4,034	(36)	102,262
Noncontrolling interests	85	(3)	149	(60)
Net income (loss) attributable to common stockholders	$ (8,277)	$ 4,031	$ 113	$ 102,202
Weighted average common shares outstanding - basic (in shares)	47,684,152	47,536,320	47,664,709	47,523,688
Weighted average common shares outstanding - diluted (in shares)	47,684,152	47,875,418	48,476,933	47,727,634
Basic income (loss) per common share (in dollars per share)	$ (0.17)	$ 0.08	$ 0	$ 2.14
Diluted income (loss) per common share (in dollars per share)	(0.17)	0.08	0	2.13
Distributions declared per common share (in dollars per share)	$ 0.18	$ 0.18	$ 0.36	$ 0.36
Comprehensive income (loss):
Other comprehensive income (loss): unrealized income (loss) on interest rate derivatives	$ 1,984	$ (1,301)	$ 7,422	$ 768
Comprehensive income (loss)	(6,378)	2,733	7,386	103,030
Comprehensive (income) loss attributable to noncontrolling interests	84	(2)	146	(60)
Comprehensive income (loss) attributable to common stockholders	$ (6,294)	$ 2,731	$ 7,532	$ 102,970

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Changes in Equity (unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Cumulative Distributions and Net Loss Attributable to Common Stockholders	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Increase (Decrease) in Equity
Cumulative effect of changes in accounting principles			$ 290	$ (290)
Beginning balance, restated	$ 620,516	$ 5	2,606,388	(1,986,805)	$ (1,042)	$ 1,970
Beginning balance at Dec. 31, 2016	620,516	$ 5	2,606,098	(1,986,515)	(1,042)	1,970
Beginning balance (in shares) at Dec. 31, 2016		47,473
Increase (Decrease) in Equity
Net income (loss)	102,262			102,202		60
Unrealized gain on interest rate derivatives	768				768
Share based compensation, net	1,604		1,872			(268)
Share-based compensation, net (in shares)		69
Contributions by noncontrolling interests	438					438
Distributions declared, Common stock ($0.36 and $0.36 per share for the six months ended June 30, 2018 and 2017, respectively)	(17,217)			(17,217)
Distributions declared, Noncontrolling interests	(10)					(10)
Deconsolidation of investment	(1,500)					(1,500)
Ending balance (in shares) at Jun. 30, 2017		47,542
Ending balance at Jun. 30, 2017	706,861	$ 5	2,608,260	(1,901,820)	(274)	690
Increase (Decrease) in Equity
Cumulative effect of changes in accounting principles	1,460			635	825
Beginning balance, restated	679,031	5	2,609,540	(1,936,325)	5,043	768
Beginning balance at Dec. 31, 2017	677,571	$ 5	2,609,540	(1,936,960)	4,218	768
Beginning balance (in shares) at Dec. 31, 2017		47,623
Increase (Decrease) in Equity
Net income (loss)	(36)			113		(149)
Issuance of common stock, net (in shares)		901
Issuance of common stock, net	20,871		20,871
Unrealized gain on interest rate derivatives	7,422				7,419	3
Share based compensation, net	1,955		2,224			(269)
Share-based compensation, net (in shares)		51
Contributions by noncontrolling interests	2,604					2,604
Distributions declared, Common stock ($0.36 and $0.36 per share for the six months ended June 30, 2018 and 2017, respectively)	(17,254)			(17,254)
Distributions declared, Noncontrolling interests	(3)					(3)
Ending balance (in shares) at Jun. 30, 2018		48,575
Ending balance at Jun. 30, 2018	$ 694,590	$ 5	$ 2,632,635	$ (1,953,466)	$ 12,462	$ 2,954

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Changes in Equity (unaudited) (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Stockholders' Equity [Abstract]
Distributions declared per common share (in dollars per share)	$ 0.18	$ 0.18	$ 0.36	$ 0.36

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net income (loss)	$ (36)	$ 102,262
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Gain on sale of assets	(11,924)	(92,012)
Gain on remeasurement of investment in unconsolidated entities	(11,090)	(14,168)
Loss on early extinguishment of debt	8,988	545
Hedge ineffectiveness expense from derivatives	0	1
Amortization of restricted shares and units	2,164	1,933
Depreciation and amortization	51,750	47,181
Amortization of lease intangibles	(134)	(286)
Amortization of above- and below-market rent	(2,941)	(1,788)
Amortization of deferred financing fees	762	1,679
Equity in operations of investments	(287)	(6,300)
Ownership portion of fees from unconsolidated entities	80	194
Distributions from investments	10	8,963
Change in accounts receivable	(3,695)	(4,207)
Change in prepaid expenses and other assets	307	(222)
Change in lease commissions	(2,861)	(5,368)
Change in other lease intangibles	3	(387)
Change in accounts payable and accrued liabilities	(11,725)	(13,515)
Change in other liabilities	350	1,971
Cash provided by operating activities	19,721	26,476
Cash flows from investing activities
Escrow deposits	(3,350)	(6,000)
Return of investments	1,711	23,433
Purchases of real estate	(99,154)	(93,011)
Investments in unconsolidated entities	(843)	(10,732)
Capital expenditures for real estate	(17,559)	(17,720)
Capital expenditures for real estate under development	(37,788)	(13,992)
Proceeds from sales of assets	141,149	330,045
Cash provided by (used in) investing activities	(15,834)	212,023
Cash flows from financing activities
Financing costs	(3,217)	(1,933)
Proceeds from notes payable	735,000	145,000
Payments on notes payable	(737,761)	(338,088)
Payments for early extinguishment of debt	(3,632)	(436)
Issuance of common stock	21,302	0
Costs associated with issuance of common stock	(431)	0
Transfer of common stock	(210)	(329)
Distributions paid to common stockholders	(17,254)	(25,811)
Distributions paid to noncontrolling interests	(3)	(17)
Contributions from noncontrolling interests	2,454	438
Cash used in financing activities	(3,752)	(221,176)
Net change in cash, cash equivalents, and restricted cash	135	17,323
Cash, cash equivalents, and restricted cash at beginning of period	22,310	22,393
Cash, cash equivalents, and restricted cash at end of period	$ 22,445	$ 39,716

Business

Business	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business	Business Organization TIER REIT, Inc. is a publicly traded (NYSE: TIER), self-managed, Dallas-based real estate investment trust focused on owning quality, well-managed commercial office properties in dynamic markets throughout the U.S. As used herein, “TIER REIT,” the “Company,” “we,” “us,” or “our” refers to TIER REIT, Inc. and its subsidiaries unless the context otherwise requires. TIER REIT’s vision is to be the premier owner and operator of best-in-class office properties in TIER 1 submarkets, which are primarily higher density and amenity-rich locations within select, high-growth metropolitan areas that offer a walkable experience to various amenities. Our mission is to provide unparalleled, TIER ONE Property Services to our tenants and outsized total return through stock price appreciation and dividend growth to our stockholders. TIER REIT was incorporated in June 2002 as a Maryland corporation and has elected to be treated, and currently qualifies, as a real estate investment trust, or REIT, for federal income tax purposes. As of June 30, 2018 , we owned interests in 18 operating office properties, one non-operating property, and three development properties. Our operating properties are located in six markets throughout the United States. Substantially all of our business is conducted through Tier Operating Partnership LP (“Tier OP”), a Texas limited partnership. Our wholly-owned subsidiary, Tier GP, Inc., a Delaware corporation, is the sole general partner of Tier OP. Our direct and indirect wholly-owned subsidiaries, Tier Business Trust, a Maryland business trust, and Tier Partners, LLC, a Delaware limited liability company, are limited partners that together with Tier GP, Inc. own all of Tier OP.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Interim Unaudited Financial Information The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2017, which was filed with the Securities and Exchange Commission (“SEC”) on February 12, 2018. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been omitted from this report on Form 10-Q pursuant to the rules and regulations of the SEC. The results for the interim periods shown in this report are not necessarily indicative of future financial results. The accompanying condensed consolidated balance sheets as of June 30, 2018 , and December 31, 2017 , and condensed consolidated statements of operations and comprehensive income (loss), changes in equity, and cash flows for the periods ended June 30, 2018 and 2017 , have not been audited by our independent registered public accounting firm. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments necessary to present fairly our financial position as of June 30, 2018 , and December 31, 2017 , and our results of operations and our cash flows for the periods ended June 30, 2018 and 2017 . These adjustments are of a normal recurring nature. We have evaluated subsequent events for recognition or disclosure in our condensed consolidated financial statements. Summary of Significant Accounting Policies Described below are certain of our significant accounting policies. The disclosures regarding several of the policies have been condensed or omitted in accordance with interim reporting regulations specified by Form 10-Q pursuant to the rules and regulations of the SEC. Please see our consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for a complete listing of our significant accounting policies. Real Estate The following is a summary of our buildings and improvements and related lease intangibles as of June 30, 2018 , and December 31, 2017 (in thousands): Lease Intangibles Assets Liabilities Acquired Above-Market Leases Acquired Below-Market Leases Buildings and Improvements Other Lease Intangibles as of June 30, 2018 Cost $ 1,642,748 $ 173,283 $ 4,857 $ (61,205 ) Less: accumulated depreciation and amortization (482,475 ) (67,405 ) (4,677 ) 35,295 Net $ 1,160,273 $ 105,878 $ 180 $ (25,910 ) Lease Intangibles Assets Liabilities Acquired Above-Market Leases Acquired Below-Market Leases Buildings and Improvements Other Lease Intangibles as of December 31, 2017 Cost $ 1,514,544 $ 146,926 $ 4,857 $ (50,399 ) Less: accumulated depreciation and amortization (453,126 ) (60,298 ) (4,438 ) 32,457 Net $ 1,061,418 $ 86,628 $ 419 $ (17,942 ) We amortize the value of in-place leases, in-place tenant improvements, and in-place leasing commissions to expense over the initial term of the respective leases. The tenant relationship values are amortized to expense over the tenants’ respective initial lease terms and any anticipated renewal periods, but in no event does the amortization period for intangible assets or liabilities exceed the remaining depreciable life of the building. Should a tenant terminate its lease, the unamortized portion of the acquired lease intangibles related to that tenant would be charged to expense. The estimated remaining average useful lives for acquired lease intangibles range from an ending date of July 2018 to an ending date of November 2027. Anticipated amortization associated with acquired lease intangibles for each of the following five years is as follows (in thousands): July 2018 - December 2018 3,594 2019 7,119 2020 6,274 2021 5,025 2022 4,323 Hurricane Harvey In August 2017, One & Two Eldridge Place and Three Eldridge Place (collectively known as the “Eldridge Properties”), located in Houston, Texas, experienced flood-related damage as a result of Hurricane Harvey and its aftermath. By early January 2018, all of the properties were fully operational. We carry comprehensive property, casualty, flood, and business interruption insurance that we anticipate will cover our losses at the properties, subject to a deductible. In the third quarter of 2017, we recognized approximately $15.0 million for the write-off of the net book value of damaged assets, and we have incurred approximately $11.4 million of restoration expenses from August 2017 through June 2018. The write-off of the net book value of damaged assets and the restoration expenses incurred have been fully offset by an estimated insurance recovery. Since we determined receipt of insurance proceeds is probable, the estimated insurance recovery is recorded as a receivable and is included in “accounts receivable, net” on our condensed consolidated balance sheets. Through June 30, 2018 , we have received approximately $7.1 million of this insurance recovery. To the extent that insurance proceeds ultimately exceed the net book value of damaged assets plus the restoration expenses incurred, the excess (net of the deductible) will be reflected as income in the period insurance proceeds are received or when receipt is deemed probable to occur. During the three and six months ended June 30, 2018 , we provided rent abatements of approximately $0.8 million and $ 4.7 million , respectively, to tenants as a result of Hurricane Harvey. These abatements were a reduction to “rental revenue” on our condensed consolidated statements of operations and comprehensive income (loss) for the three and six months ended June 30, 2018 . For the three and six months ended June 30, 2018, these rent abatements were offset by approximately $0.4 million and $3.7 million , respectively, of business interruption insurance proceeds (net of estimated saved expenses). We anticipate we will receive remaining business interruption insurance proceeds in subsequent quarters. Cash, Cash Equivalents, and Restricted Cash We consider investments in highly-liquid money market funds or investments with original maturities of three months or less to be cash equivalents. Restricted cash includes restricted money market accounts, as required by our lenders or by leases, for anticipated tenant improvements, property taxes and insurance, certain tenant security deposits, and additional loan security reserves. The following is a summary of our total cash, cash equivalents, and restricted cash as presented in our statements of cash flows for the six months ended June 30, 2018 and 2017 (in thousands): June 30, June 30, Cash and cash equivalents $ 8,359 $ 28,763 Restricted cash 14,086 10,953 Total cash, cash equivalents, and restricted cash $ 22,445 $ 39,716 Accounts Receivable, net The following is a summary of our accounts receivable as of June 30, 2018 , and December 31, 2017 (in thousands): June 30, December 31, Straight-line rental revenue receivable $ 53,674 $ 57,372 Insurance receivable 19,717 18,826 Tenant receivables 6,217 4,221 Non-tenant receivables 1,564 893 Allowance for doubtful accounts (417 ) (183 ) Total $ 80,755 $ 81,129 Our allowance for doubtful accounts is an estimate based on management’s evaluation of accounts where it has determined that a tenant may not meet its financial obligations. In these situations, management uses its judgment, based on the facts and circumstances, and records a reserve for that tenant against amounts due to reduce the receivable to an amount it believes is collectible. These reserves are reevaluated and adjusted as additional information becomes available. Investments in Unconsolidated Entities Investments in unconsolidated entities consist of our noncontrolling interests in properties. We account for these investments using the equity method of accounting in accordance with GAAP. We use the equity method of accounting when we have significant influence, but not control, of the operating and financial decisions of these investments and thereby have some responsibility to create a return on our investment. The equity method of accounting requires these investments to be initially recorded at cost and subsequently increased (decreased) for our share of net income (loss), including eliminations for our share of inter-company transactions, and increased (decreased) for contributions (distributions). To the extent that we contribute assets to an unconsolidated entity, our investment in the unconsolidated entity is recorded at our cost basis in the assets that were contributed to the entity. To the extent that our cost basis is different than the basis reflected at the entity level, the basis difference is generally amortized over the life of the related asset and included in our share of equity in operations of investments. For unconsolidated investments that have properties under development, we capitalize interest expense to our investment basis using our weighted average interest rate of consolidated debt. Capitalization begins when we are engaged in the activities necessary to get the property ready for its intended use. We cease capitalization when the development is completed and ready for its intended use or if the intended use changes such that capitalization is no longer appropriate. For the six months ended June 30, 2018 and 2017, we capitalized interest expense of approximately $0.6 million and $0.7 million , respectively, for unconsolidated entities with properties under development, which is included in our investments in unconsolidated entities on our condensed consolidated balance sheets. Noncontrolling Interests Noncontrolling interests consists of our third-party partners’ proportionate share of equity in certain consolidated real estate properties and restricted stock units issued to our independent directors. Revenue Recognition Our rental revenue primarily consists of revenue generated from leases. We recognize rental income generated from all leases of consolidated real estate assets on a straight-line basis over the terms of the respective leases, including the effect of rent holidays, if any. For contracts with customers (as defined by GAAP), we recognize revenue when we transfer promised goods or services to a customer in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Our revenue from contracts with customers primarily consists of parking income, development fee income, and gain on sale of assets. Parking income - Parking income is primarily generated (1) through contractual arrangements with management companies that operate our parking garages and remit the monthly revenue collected to us or (2) directly through tenant leases. Revenue is recognized at a point in time upon the performance of services. Accounts receivable are recorded for services provided in advance of receiving payment. Management applies judgment in determining whether we are the principal or agent in those arrangements with management companies. We report revenue and expenses from these arrangements on a gross basis since we control the fulfillment of the promise to provide the service. Development fee income - We serve as a development manager for development projects owned by unconsolidated entities in which we have an ownership interest. Development fees are paid monthly and structured based on costs that approximate the percentage of construction completed. Our performance obligation is therefore satisfied over time, and we recognize development fee income based on progress of the developments. Gain on sale of assets - Upon the disposition of a property, we recognize a gain or loss at a point in time when we determine control of the underlying asset has been transferred to the buyer. Our performance obligation is generally satisfied at closing of the transaction. Any continuing involvement is analyzed as a separate performance obligation in the contract and a portion of the sales price is allocated to each performance obligation. When the performance obligation related to the continuing involvement is satisfied, the sales price allocated to it is recognized. There is significant judgment applied to estimate the amount of any variable consideration identified within the sales price and assess its probability of occurrence based on current market information, historical transactions, and forecasted information that is reasonably available.

New Accounting Pronouncements

New Accounting Pronouncements	6 Months Ended
	Jun. 30, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements Recently Adopted Accounting Pronouncements In May 2014, the FASB issued guidance to clarify the principles for recognizing revenue and to develop a common revenue standard for GAAP and International Financial Reporting Standards. The standard outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. Lease contracts are excluded from this revenue recognition criteria; however, the sale of real estate is required to follow the new model. Expanded quantitative and qualitative disclosures regarding the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers are required under the guidance. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2017. The guidance permits two implementation approaches, one requiring retrospective application of the new standard with restatement of prior years, or full retrospective, and one requiring prospective application of the new standard with disclosure of results under old standards, or modified retrospective. We adopted this guidance on January 1, 2018, using the modified retrospective approach applied to those contracts which were not completed as of January 1, 2018. The most material potential impact from adoption relates to how revenue is recognized for sales of real estate with continuing involvement. Prior to the adoption, profit for such sales transactions was recognized and then reduced by the maximum exposure to loss related to the nature of the continuing involvement at the time of sale. Under the new guidance, any continuing involvement must be analyzed as a separate performance obligation in the contract and a portion of the sales price allocated to each performance obligation. When the performance obligation related to the continuing involvement is satisfied, the sales price allocated to it is recognized. Upon adoption, we recorded a cumulative-effect adjustment to decrease opening cumulative distributions and net loss attributable to common stockholders by approximately $1.5 million . The adjustment represents a gain on sale that was deferred under the previous guidance. We determined since control of the underlying asset was transferred to the buyer at closing of the transaction, the gain was recognizable at the time of sale. Our internal controls with respect to accounting for real estate sales have been updated accordingly. The adoption of this guidance resulted in no other changes with respect to the timing of revenue recognition or internal controls related to our other revenue from contracts with customers which include primarily parking income and development fee income. The additional disclosures required under the guidance related to our revenue from contracts with customers are provided in Footnote 12. In August 2016, the FASB issued amended guidance on the classification of certain cash receipts and payments in the statement of cash flows. Of the eight types of cash flows discussed in the new standard, the classification of debt prepayment and debt extinguishment costs as financing outflows impact our financial statements as these items were previously reflected as operating outflows. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2017. We adopted this guidance on January 1, 2018, and the condensed consolidated statement of cash flows for the six months ended June 30, 2017, reflects the reclassification of approximately $0.4 million of payments for debt extinguishment costs from cash provided by operating activities to cash used in financing activities. In February 2017, the FASB issued updated guidance that clarifies the scope of asset derecognition guidance, adds guidance for partial sales of nonfinancial assets, and clarifies recognizing gains and losses from the transfer of nonfinancial assets in contracts with noncustomers. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2017. The adoption of this guidance on January 1, 2018, did not have a material impact on our financial statements or disclosures. In May 2017, the FASB issued updated guidance on applying modification accounting to changes in the terms or conditions of a share-based payment award. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2017. The adoption of this guidance on January 1, 2018, did not have a material impact on our financial statements or disclosures. In August 2017, the FASB issued updated guidance to simplify the application of hedge accounting, increase transparency as to the scope and results of hedging programs, and result in a more accurate portrayal of the economics of an entity’s risk management activities in its financial statements. The transition guidance provides the option of early adoption using a modified retrospective transition method in any interim period after issuance of the update, or alternatively requires adoption for fiscal years beginning after December 15, 2018. We early adopted this guidance using the modified retrospective approach on January 1, 2018, and recorded a cumulative-effect adjustment to increase accumulated other comprehensive income with a corresponding increase to cumulative distributions and net loss attributable to common stockholders of approximately $0.8 million to eliminate hedge ineffectiveness income previously recognized. New Accounting Pronouncements to be Adopted In February 2016, the FASB issued updated guidance which sets out revised principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The guidance requires lessees to recognize assets and liabilities for operating leases with lease terms greater than twelve months on the balance sheet. The guidance modifies lessors’ classification criteria for leases and the accounting for sales-type and direct financing leases. The guidance also makes changes to lessor accounting and reporting, specifically the classification of lease components and non-lease components, such as services provided to tenants. New disclosures regarding the amount, timing, and uncertainty of cash flows arising from leases are also required. In July 2018, the FASB issued updated guidance that provides lessors a practical expedient to not separate non-lease components from associated lease components when certain criteria are met. The combined component is accounted for under the revenue standard if the non-lease component is the predominant component of the combined component; otherwise, the combined component is accounted for as an operating lease in accordance with the new leases standard. The guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2018, with early adoption permitted and was initially required to be adopted using the modified retrospective approach. However, the updated guidance also provides a transition option that allows entities to apply the standard at the adoption date and recognize a cumulative-effect adjustment to opening retained earnings in the period of adoption. We expect to adopt this guidance effective January 1, 2019, and elect to apply the transition option and the practical expedients provided by this standard. Upon adoption, we will recognize a lease liability and a right-of-use asset for operating leases where we are the lessee, such as ground leases and office equipment leases. In June 2016, the FASB issued amended guidance which requires measurement and recognition of expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. This is different from the current guidance as this will require immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets. Financial assets that are measured at amortized cost will be required to be presented at the net amount expected to be collected with an allowance for credit losses deducted from the amortized cost basis. Generally, the pronouncement requires a modified retrospective method of adoption. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2019, with early adoption permitted. We are currently evaluating the impact this guidance will have on our financial statements when adopted.

Real Estate Activities

Real Estate Activities	6 Months Ended
	Jun. 30, 2018
Real Estate Activities [Abstract]
Real Estate Activities	Real Estate Activities Sales of Real Estate The following table presents our sales of real estate for the six months ended June 30, 2018 (in thousands): Property Name Date of Sale Location Rentable Square Footage Contract Sale Price Proceeds from Sale 500 East Pratt 02/13/18 Baltimore, MD 280 $ 60,000 $ 56,528 Centreport Office Center 02/22/18 Fort Worth, TX 133 12,696 12,421 Loop Central 03/27/18 Houston, TX 575 72,982 71,978 988 $ 145,678 $ 140,927 Properties that have been sold contributed income of less than $0.1 million and approximately $0.8 million to our net loss for the three and six months ended June 30, 2018, respectively. Properties that have been sold contributed income of approximately $1.8 million and $3.5 million to our net income for the three and six months ended June 30, 2017, respectively. These amounts exclude any gains on the sales of these properties. Acquisitions of Real Estate On January 4, 2018, we acquired a 96.5% initial economic interest in Domain Point for a contract purchase price of approximately $73.8 million (at 100% ). We own a 90% interest in the entity that owns Domain Point. Domain Point is located in Austin, Texas, adjacent to our other Domain office properties and includes two buildings with 240,000 rentable square feet (combined). Assets acquired and liabilities assumed were recorded at their relative fair values and include lease intangible assets of approximately $9.3 million and acquired below-market leases of approximately $2.8 million . The estimated remaining average useful lives for these acquired lease intangibles range from an ending date of September 2018 to an ending date of April 2022. On March 30, 2018, we acquired the remaining 50% interest in Domain Junction 8 Venture LLC, the entity that owns Domain 8, increasing our ownership interest in this property to 100% , for a contract purchase price of approximately $92.8 million , which includes the assumption of approximately $44.9 million in mortgage debt. As a result of obtaining a controlling interest in the entity, we recognized a gain of approximately $11.1 million from the remeasurement of our previously held equity interest at fair value. Assets acquired and liabilities assumed were recorded at their relative fair values upon consolidation of the property, and include lease intangible assets of approximately $21.3 million and acquired below-market leases of approximately $8.3 million . The estimated remaining average useful lives for these acquired lease intangibles range from having an ending date of May 2025 to an ending date of November 2027. Real Estate Held for Sale We had no properties held for sale as of June 30, 2018 . 500 East Pratt (sold in February 2018) was held for sale as of December 31, 2017. The major classes of assets and obligations associated with real estate held for sale as of December 31, 2017, were as follows (in thousands): December 31, 2017 Buildings and improvements, net of approximately $29.0 million in accumulated depreciation $ 45,396 Accounts receivable and other assets 3,335 Lease intangibles, net of approximately $5.6 million in accumulated amortization 2,830 Other intangible assets, net of approximately $1.2 million in accumulated amortization 1,787 Assets associated with real estate held for sale $ 53,348 Acquired below-market leases, net of approximately $1.3 million in accumulated amortization $ 364 Other liabilities 1,990 Obligations associated with real estate held for sale $ 2,354

Real Estate Under Development

Real Estate Under Development	6 Months Ended
	Jun. 30, 2018
Real Estate Under Development [Abstract]
Real Estate Under Development	Real Estate Under Development When we are engaged in activities to get a potential development ready for its intended use, we capitalize interest, property taxes, insurance, ground lease payments, and direct construction costs. For the six months ended June 30, 2018 , we capitalized a total of approximately $43.4 million , including approximately $1.8 million of interest. For the six months ended June 30, 2017 , we capitalized a total of approximately $8.9 million , which included approximately $0.6 million of interest. These costs are classified as real estate under development on our condensed consolidated balance sheets until such time that the development is complete.

Investments in Unconsolidated E

Investments in Unconsolidated Entities	6 Months Ended
	Jun. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in Unconsolidated Entities	Investments in Unconsolidated Entities We participate in real estate ventures for the purpose of acquiring and developing office properties in which we may or may not have a controlling financial interest. Our investments in unconsolidated entities consist of our noncontrolling interests in certain properties that are accounted for using the equity method of accounting. The following is a summary of our investments in unconsolidated entities as of June 30, 2018 , and December 31, 2017 (dollar amounts in thousands): Ownership Interest Unconsolidated Investment Balance Entity Name Property June 30, December 31, 2017 June 30, December 31, Domain Junction 8 Venture LLC (1)(2) Domain 8 100.00 % 50.00 % $ — $ 882 208 Nueces Street, LLC (2) Third + Shoal 47.50 % 47.50 % 31,714 30,970 Total (3) ` $ 31,714 $ 31,852 _________________ (1) On March 30, 2018, we acquired the unrelated third party’s 50% interest in Domain Junction 8 Venture LLC increasing our ownership interest to 100% , and this property was consolidated. (2) We evaluate our investments in unconsolidated entities in order to determine if they are variable interest entities (“VIEs”). Based on our assessment, we identified each of these entities as a VIE, but we are not the primary beneficiary, as we do not have the power to direct the activities that most significantly impact the economic performance of these entities. For VIEs in which we are not deemed to be the primary beneficiary, we continue to account for them using the equity method. The maximum amount of exposure to loss with respect to these VIEs is the carrying amount of our investment and any debt guaranteed by us. As of June 30, 2018 , and December 31, 2017 , Tier OP guaranteed 25% and 50% , respectively, of the construction loan of 208 Nueces Street, LLC, as discussed below in “Guarantees.” At June 30, 2018 , our VIEs have total assets of approximately $108.8 million and total liabilities of approximately $54.3 million . At December 31, 2017 , our VIEs had total assets of approximately $172.3 million and total liabilities of approximately $125.1 million . (3) Our investments in unconsolidated entities at June 30, 2018 , and December 31, 2017 , include basis adjustments that total approximately $5.8 million and $9.4 million , respectively. These amounts represent the aggregate difference between our historical cost basis and our equity basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differences occur from impairment of investments and upon the transfer of assets that were previously owned by us into a joint venture. In addition, capitalized interest and certain acquisition, transaction, and other costs may not be reflected in the net assets at the joint venture level. Our equity in operations of investments represents our proportionate share of the combined earnings and losses of our investments for the period of our ownership and in 2017, includes combined gains on the sales of 1325 G Street and the Colorado Building of approximately $6.7 million . For the three months ended June 30, 2018 and 2017, we recorded no income and approximately $6.6 million of income, respectively, for our share of equity in operations from our investments in unconsolidated entities. For the six months ended June 30, 2018 and 2017, we recorded income of approximately $0.3 million and approximately $6.3 million , respectively, for our share of equity in operations from our investments in unconsolidated entities. Guarantees The unconsolidated entities in which we have investments generally finance their activities with a combination of partner equity and debt financing. In 2017, 208 Nueces Street, LLC entered into a construction loan for the development of Third + Shoal, in which Tier OP guaranteed up to 50% of the outstanding principal balance. This percentage is reduced when certain conditions in the guarantee agreement are met, and as of June 30, 2018 , this percentage was 25% . The guarantee, which extends to October 2021 when the loan matures, includes a project completion guarantee and a payment guarantee covering a percentage of the outstanding loan. Additionally, there is a recourse carve-out agreement in which Tier OP guarantees the entire outstanding balance of the loan in addition to any related losses that may arise from certain violations of the joint venture’s contractual agreements, including “bad boy acts.” In these situations, we have an indemnity and contribution agreement with our partners where each partner has indemnified the other for any recourse liability resulting from claims triggered by that partner. As of June 30, 2018 , 208 Nueces Street, LLC has a loan commitment of approximately $103.8 million , of which, if the full amount of the debt obligation was borrowed, we estimate approximately $26.0 million is our maximum exposure related to the payment guarantee. As of June 30, 2018 , the outstanding balance of the construction loan for 208 Nueces Street, LLC was approximately $44.7 million , of which we estimate approximately $11.2 million is our maximum exposure related to the payment guarantee. These maximum exposure estimates do not take into account any recoveries from the underlying collateral or any reimbursement from our partners. We believe that, as of June 30, 2018 , in the event we become legally obligated to perform under the payment guarantee, the collateral in 208 Nueces Street, LLC should be sufficient to repay the obligation. If it is not, we and our partners would need to contribute additional capital to the venture.

Notes Payable, net

Notes Payable, net	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Notes Payable, net	Notes Payable, net Our notes payable, net were approximately $886.3 million as of June 30, 2018 . Approximately $279.2 million of these notes payable, net were secured by real estate assets with a carrying value of approximately $398.8 million as of June 30, 2018 . As of June 30, 2018 , all of our outstanding debt was fixed rate debt (or effectively fixed rate debt, through the use of interest rate swaps), with the exception of approximately $172.7 million . As of June 30, 2018 , the stated annual interest rates on our outstanding debt, ranged from approximately 3.16% to 6.09% . As of June 30, 2018 , the effective weighted average interest rate for our debt is approximately 3.91% . For our loan that is in default and detailed below, we incur a default interest rate that is 500 basis points higher than the stated interest rate, which resulted in an overall effective weighted average interest rate for our debt of approximately 4.19% as of June 30, 2018 , and additional interest expense of approximately $1.2 million for the six months ended June 30, 2018 . We anticipate, although we can provide no assurance, that when the property to which such loan relates is sold, or if ownership of this property is conveyed to the lender, the default interest will be forgiven. Our loan agreements generally require us to comply with certain reporting and financial covenants. As of June 30, 2018 , we were in default on a non-recourse property loan with an outstanding balance of approximately $48.2 million secured by our Fifth Third Center property located in Columbus, Ohio, which has a carrying value of approximately $31.6 million as of June 30, 2018 . A receiver was appointed for this property in March 2016. The loan had an original maturity date of July 2016, and we are currently working with the lender to dispose of this property on its behalf, although there can be no assurance regarding such disposition. As of June 30, 2018 , other than the default discussed above, we believe we were in compliance with the covenants under each of our loan agreements, including our credit facility. Excluding debt already matured as detailed above, our outstanding debt has maturity dates that range from June 2020 to January 2025. The following table provides information regarding the timing of principal payments of our notes payable, net, as of June 30, 2018 (in thousands): Principal payments due in: July 2018 - December 2018 $ 48,917 2019 1,589 2020 91,403 2021 72,402 2022 308,000 Thereafter 366,000 Less: unamortized debt issuance costs (1) (2,051 ) Notes payable, net $ 886,260 ________________ (1) Excludes approximately $3.2 million of unamortized debt issuance costs associated with the revolving line of credit because these costs are presented as an asset on our condensed consolidated balance sheets. Credit Facility We have a credit agreement through our operating partnership, Tier OP, that provides for total unsecured borrowings of up to $900.0 million , subject to our compliance with certain financial covenants. The facility consists of a $300.0 million term loan, a $275.0 million term loan, and a $325.0 million revolving line of credit. The $300.0 million term loan matures on January 17, 2025. The $275.0 million term loan matures on June 30, 2022. The revolving line of credit matures on January 18, 2022, and can be extended one additional year subject to certain conditions and payment of an extension fee. The annual interest rate on the credit facility is equal to either, at our election, (1) the “base rate” (calculated as the greatest of (i) the agent’s “prime rate”; (ii) 0.5% above the Federal Funds Effective Rate; or (iii) the LIBOR Market Index Rate plus 1.0% ) plus the applicable margin or (2) LIBOR for an interest period of one , three , or six months plus the applicable margin. The applicable margin will be determined based on the ratio of total indebtedness to total asset value and ranges from 10 basis points to 235 basis points. We have entered into interest rate swap agreements to hedge interest rates on $525.0 million of these borrowings to manage our exposure to future interest rate movements. All amounts owed are guaranteed by us and certain subsidiaries of Tier OP. As of June 30, 2018 , we had approximately $575.0 million in borrowings outstanding under the term loans, and $33.0 million in borrowings outstanding under the revolving line of credit with the ability, subject to our most restrictive financial covenants, to borrow an additional approximately $209.4 million under the facility as a whole. As of June 30, 2018 , the weighted average effective interest rate for borrowings under the credit facility as a whole, inclusive of our interest rate swaps, was approximately 3.46% .

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value, as defined by GAAP, is a market-based measurement, not an entity-specific measurement. Therefore, a fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within Levels 1 and 2 of the fair value hierarchy) and the reporting entity’s own assumptions about market participant assumptions (unobservable inputs classified within Level 3 of the fair value hierarchy) has been established. Assets and Liabilities Measured at Fair Value on a Recurring Basis Derivative financial instruments We use derivative financial instruments, such as interest rate swaps, to manage our interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis of the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. We incorporate credit valuation adjustments (“CVAs”) to appropriately reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. Although we have determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the CVAs associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by us and our counterparties. However, we have assessed the significance of the impact of the CVAs on the overall valuation of our derivative positions and have determined that they are not significant. As a result, we have determined that our derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. Unrealized gains or losses on derivatives are recorded in accumulated other comprehensive income (loss) (“OCI”) within equity at each measurement date. Our derivative financial instruments are included in “prepaid expenses and other assets” on our condensed consolidated balance sheets. The following table sets forth our financial assets and liabilities measured at fair value on a recurring basis, which equals book value, by level within the fair value hierarchy as of June 30, 2018 , and December 31, 2017 (in thousands): Basis of Fair Value Measurements Quoted Prices In Active Markets for Identical Items (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Description June 30, 2018 Derivative financial instruments: Assets $ 12,467 $ — $ 12,467 $ — December 31, 2017 Derivative financial instruments: Assets $ 5,045 $ — $ 5,045 $ — Financial Instruments not Reported at Fair Value Financial instruments held at June 30, 2018 , and December 31, 2017 , but not measured at fair value on a recurring basis include cash and cash equivalents, restricted cash, accounts receivable, notes payable, accounts payable and accrued liabilities, and other liabilities. With the exception of notes payable, the financial statement carrying amounts of these items approximate their fair values due to their short-term nature. Estimated fair values for notes payable have been determined using recent trading activity and/or bid-ask spreads and are classified as Level 2 in the fair value hierarchy. Carrying amounts of our notes payable and the related estimated fair value as of June 30, 2018 , and December 31, 2017 , are as follows (in thousands): June 30, 2018 December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value Notes payable $ 888,311 $ 891,216 $ 801,339 $ 805,786 Less: unamortized debt issuance costs (2,051 ) (6,801 ) Notes payable, net $ 886,260 $ 794,538

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities We may be exposed to the risk associated with variability of interest rates that might impact our cash flows and the results of our operations. Our objectives in using interest rate derivatives are to add stability to interest expense and to manage our exposure to interest rate movements. To accomplish this objective, we have used interest rate swaps as part of our interest rate risk management strategy. Our interest rate swaps involve the receipt of variable-rate amounts from counterparties in exchange for us making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Our hedging strategy of entering into interest rate swaps, therefore, is to eliminate or reduce, to the extent possible, the volatility of cash flows. The following table summarizes the notional values of our derivative financial instruments (in thousands) as of June 30, 2018 . The notional values provide an indication of the extent of our involvement in these instruments at June 30, 2018 , but do not represent exposure to credit, interest rate, or market risks. Type/Description Notional Value Index Strike Rate Effective Date Maturity Date Interest rate swap - cash flow hedge $ 125,000 one-month LIBOR 1.6775 % 12/31/14 10/31/19 Interest rate swap - cash flow hedge $ 125,000 one-month LIBOR 1.6935 % 04/30/15 10/31/19 Interest rate swap - cash flow hedge $ 125,000 one-month LIBOR 1.7615 % 06/30/15 05/31/22 Interest rate swap - cash flow hedge $ 150,000 one-month LIBOR 1.7695 % 06/30/15 05/31/22 The table below presents the fair value of our derivative financial instruments, included in “prepaid expenses and other assets” on our condensed consolidated balance sheets, as of June 30, 2018 , and December 31, 2017 (in thousands): Derivatives Designated as Hedging Instruments: Derivative Assets June 30, December 31, Interest rate swaps $ 12,467 $ 5,045 The tables below present the effect of the change in fair value of derivative financial instruments in our condensed consolidated statements of operations and comprehensive income (loss) for the three and six months ended June 30, 2018 and 2017 (in thousands): Derivatives in Cash Flow Hedging Relationship Gain (loss) recognized in OCI on derivatives Three Months Ended Six Months Ended June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Interest rate swaps $ 1,984 $ (1,301 ) $ 7,422 $ 768 Amount reclassified from OCI into income Three Months Ended Six Months Ended Location June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Interest expense (1) $ (259 ) $ 953 $ (100 ) $ 2,199 ______________ (1) Increases (decreases) in fair value as a result of accrued interest associated with our swap transactions are recorded in accumulated OCI and subsequently reclassified into income. Such amounts are shown net in the condensed consolidated statements of changes in equity and offset dollar for dollar. Total interest expense presented in the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) in which the effects of cash flow hedges are recorded Three Months Ended Six Months Ended Location June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Interest expense $ 8,369 $ 8,235 $ 16,478 $ 17,015 Amounts reported in accumulated OCI related to derivatives will be reclassified to interest expense as interest payments and accruals are made on our variable-rate debt. During the next twelve months, we estimate that approximately $3.5 million will be reclassified as a decrease to interest expense. We have agreements with our derivative counterparties that contain provisions where if we default on any of our indebtedness for at least 30 days, during which time such default has not been remedied, and in all cases provided that the aggregate amount of all such defaults is not less than $10.0 million for recourse debt or $75.0 million for non-recourse debt, then we could also be declared in default on our derivative obligations.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies As of June 30, 2018 , we had commitments of approximately $17.2 million for future building improvements, tenant improvements, and leasing commissions. We have employment agreements with our five named executive officers. The term of each employment agreement ends on February 10, 2020, provided that the term will automatically continue for an additional one -year period unless either party provides 60 days written notice of non-renewal prior to the expiration of the initial term. The agreements provide for lump sum payments and an immediate lapse of restrictions on compensation received under the long-term incentive plan upon termination of employment without cause. As a result, in the event we terminated all of these agreements without cause as of June 30, 2018 , we would have recognized approximately $14.3 million in related compensation expense.

Equity

Equity	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Equity	Equity Stock Plans Our 2015 Equity Incentive Plan allows for, and our 2005 Incentive Award Plan allowed for, equity-based incentive awards to be granted to our employees, non-employee directors, and key persons as detailed below: Restricted stock units held by independent directors. We have outstanding restricted stock units (“RSUs”) held by our independent directors. These units vest 13 months after the grant date. Subsequent to vesting, the restricted stock units will be converted to an equivalent number of shares of common stock upon the earlier to occur of the following events or dates: (i) separation from service for any reason other than cause; (ii) a change in control of the Company; (iii) death; or (iv) July 2019. Expense is measured at the grant date based on the estimated fair value of the award and is recognized over the vesting period. Any forfeitures of awards are recognized as they occur. The following is a summary of the number of outstanding RSUs held by our independent directors as of June 30, 2018 and 2017 : June 30, 2018 June 30, 2017 Units Weighted Average Price per unit Units Weighted Average Price per unit Outstanding at the beginning of the year 19,672 $ 17.03 39,255 $ 16.45 Issued 12,910 $ 23.24 19,672 $ 17.03 Converted (19,672 ) $ 17.03 (29,307 ) $ 16.92 Outstanding at the end of the period (1) 12,910 $ 23.24 29,620 $ 16.38 _____________ (1) As of June 30, 2018 , none of the RSUs held by our independent directors are vested. Restricted stock units held by employees. We have outstanding RSUs held by employees. These units vest from December 2018 to December 2020 at which time the units will be converted into a number of shares of common stock, which could range from zero shares to 200% of the issued number of units. The actual number of shares of common stock issued will be based on our annualized total stockholder return (“TSR”) percentage as compared to three metrics: our TSR on a predetermined absolute basis, the TSR of the constituent companies of the NAREIT Office Index (unweighted), and the TSR of a select group of peer companies. The following is a summary of the number of outstanding RSUs held by our employees as of June 30, 2018 and 2017 : June 30, 2018 June 30, 2017 Units Weighted Average Price per unit Units Weighted Average Price per unit Outstanding at the beginning of the year 208,620 $ 16.59 111,063 $ 15.26 Issued 129,188 $ 17.24 97,557 $ 18.10 Outstanding at the end of the period 337,808 $ 16.84 208,620 $ 16.59 Compensation cost is measured at the grant date, based on the estimated fair value of the award (ranging from $16.80 per unit to $20.95 per unit) as determined by a Monte Carlo simulation-based model using the assumptions outlined in the table below. Any forfeitures of awards are recognized as they occur. Assumption Value Expected volatility 24% - 26% Risk-free interest rate 1.15% - 2.37% Expected term 35 months Expected dividend yield 3.7% - 4.5% Restricted stock. We have outstanding restricted stock held by employees. Restrictions on outstanding shares lapse based on various lapse schedules and range from December 2018 to December 2020. Compensation cost is measured at the grant date based on the estimated fair value of the award and is recognized as expense over the service period based on a tiered lapse schedule. Any forfeitures of awards are recognized as they occur. The following is a summary of the number of shares of restricted stock outstanding as of June 30, 2018 and 2017 : June 30, 2018 June 30, 2017 Shares Weighted Average Price per share Shares Weighted Average Price per share Outstanding at the beginning of the year 180,791 $ 20.47 246,805 $ 20.74 Issued 125,558 $ 17.24 121,860 $ 17.88 Forfeitures (4,914 ) $ 17.10 (20,089 ) $ 17.53 Restrictions lapsed (41,062 ) $ 26.23 (57,553 ) $ 25.64 Outstanding at the end of the period 260,373 $ 18.07 291,023 $ 18.79 For the three months ended June 30, 2018 and 2017 , we recognized a total of approximately $1.2 million and $1.0 million , respectively, for compensation expense related to the amortization of all of the equity-based incentive awards outlined above. For the six months ended June 30, 2018 and 2017 , we recognized a total of approximately $2.2 million and $1.9 million , respectively, for compensation expense related to the amortization of all of the equity-based incentive awards outlined above. As of June 30, 2018 , the total remaining compensation cost on unvested awards was approximately $5.9 million , with a weighted average remaining contractual life of approximately 1.4 years. ATM Program On May 10, 2017, we established an at-the-market equity offering program (the “ATM Program”) pursuant to which we may issue and sell shares of our common stock having an aggregate offering price of up to $125.0 million in amounts and at times as we determine from time to time. We have no obligation to sell any of such shares. Actual sales will depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions, the trading price of our common stock, our determinations of the appropriate sources of funding for the Company, and potential uses of funding available to us. We intend to use the net proceeds from the offering of such shares, if any, for general corporate purposes, which may include future acquisitions, development, and repayment of indebtedness, including borrowings under our credit facility. During the three months ended June 30, 2018 , we issued 901,300 shares of common stock under the ATM Program, generating proceeds of approximately $20.9 million , net of approximately $0.3 million of commissions and approximately $0.1 million of issuance costs. Subsequent to June 30, 2018, we issued 1,940,251 shares of common stock under the ATM Program, generating proceeds of approximately $44.8 million , net of approximately $0.6 million of commissions and approximately $0.2 million of issuance costs.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2018
Revenues [Abstract]
Revenue	Revenue We recognize rental income generated from all leases of consolidated real estate assets on a straight-line basis over the terms of the respective leases, including the effect of rent holidays, if any. The total net increase to rental revenue due to straight-line rent adjustments for the three months ended June 30, 2018 and 2017 , was approximately $0.8 million and $2.0 million , respectively. The total net increase to rental revenue due to straight-line rent adjustments for the six months ended June 30, 2018 and 2017 , was approximately $1.3 million and $3.8 million , respectively. When a tenant exceeds its tenant improvement allowance, this amount is reimbursed to us and recorded as a deferred rent liability, which is recognized as rental revenue over the life of the lease. The total net increase to rental revenue due to this deferred rent for the three months ended June 30, 2018 and 2017 , was approximately $0.4 million and $0.4 million , respectively. The total net increase to rental revenue due to this deferred rent for the six months ended June 30, 2018 and 2017 , was approximately $0.8 million and $1.0 million , respectively. Our rental revenue also includes amortization of acquired above- and below-market leases. The total net increase to rental revenue due to the amortization of acquired above- and below-market leases for the three months ended June 30, 2018 and 2017 , was approximately $1.7 million and $0.9 million , respectively. The total net increase to rental revenue due to the amortization of acquired above- and below-market leases for the six months ended June 30, 2018 and 2017 , was approximately $2.9 million and $1.8 million , respectively. Revenues relating to lease termination fees are recognized on a straight-line basis amortized from the time that a tenant’s right to occupy the leased space is modified through the end of the revised lease term. For the three months ended June 30, 2018 and 2017 , we recognized lease termination fees of approximately $0.4 million and $0.1 million , respectively. For the six months ended June 30, 2018 and 2017 , we recognized lease termination fees of approximately $0.7 million and $0.2 million , respectively. Included in our rental revenue is parking income of approximately $2.3 million and $2.0 million for the three months ended June 30, 2018 and 2017, respectively, and $4.6 million and $3.9 million for the six months ended June 30, 2018 and 2017, respectively, which represents revenue from contracts with customers. Gain (loss) on sale of assets, which also represents revenue from contracts with customers, was a loss of approximately $0.1 million and a gain of approximately $1.3 million for the three months ended June 30, 2018 and 2017, respectively, and gains of approximately $11.9 million and $92.0 million for the six months ended June 30, 2018 and 2017, respectively. We had no significant development fee income for the three or six months ended June 30, 2018 . We had development fee income of approximately $0.2 million for the three and six months ended June 30, 2017. Accounts receivables from contracts with customers were approximately $0.9 million and $0.6 million as of June 30, 2018 and December 31, 2017, respectively.

Net Income (Loss) per Common Sh

Net Income (Loss) per Common Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Income (Loss) per Common Share	Net Income (Loss) per Common Share Net income (loss) per common share is calculated using the two-class method, which requires the allocation of undistributed net income between common and participating stockholders. All outstanding restricted stock awards containing rights to non-forfeitable distributions are considered participating securities for this calculation. In periods of net loss, no loss is allocated to participating securities because our participating securities do not have a contractual obligation to share in our losses. The following table reflects the calculation of basic and diluted net income (loss) per common share for the three and six months ended June 30, 2018 and 2017 (in thousands, except per share data): Three Months Ended Six Months Ended June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Numerator: Net income (loss) attributable to common stockholders $ (8,277 ) $ 4,031 $ 113 $ 102,202 Less: net income allocated to participating securities — — — (611 ) Numerator for basic net income (loss) per share $ (8,277 ) $ 4,031 $ 113 $ 101,591 Add: undistributed net income allocated to participating securities — — — 506 Less: undistributed net income re-allocated to participating securities — — — (504 ) Numerator for diluted net income (loss) per share (1) $ (8,277 ) $ 4,031 $ 113 $ 101,593 Denominator: Weighted average common shares outstanding - basic 47,684 47,536 47,665 47,524 Effect of dilutive securities — 339 812 204 Weighted average common shares outstanding - diluted 47,684 47,875 48,477 47,728 Basic net income (loss) per common share $ (0.17 ) $ 0.08 $ 0.00 $ 2.14 Diluted net income (loss) per common share $ (0.17 ) $ 0.08 $ 0.00 $ 2.13 Securities excluded from weighted average common shares outstanding-diluted because their effect would be anti-dilutive 992 29 17 29 _______________ (1) In periods where there is no undistributed net income to allocate to participating securities, the treasury stock method is used to calculate dilutive securities.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	6 Months Ended
	Jun. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Supplemental cash flow information is summarized below for the six months ended June 30, 2018 and 2017 (in thousands): Six Months Ended June 30, 2018 June 30, 2017 Interest paid, net of amounts capitalized $ 14,211 $ 12,695 Income taxes paid $ 758 $ 403 Non-cash investing activities: Property and equipment additions in accounts payable and accrued liabilities $ 17,382 $ 7,816 Liabilities assumed through the purchase of real estate $ 7,028 $ 3,267 Escrow deposits applied to purchase of real estate $ 21,350 $ 14,000 Escrow deposit applied to purchase of real estate from noncontrolling interest $ 150 $ — Sale of real estate and lease intangibles to unconsolidated joint venture $ — $ 13,804 Acquisition of controlling interest in unconsolidated entity $ 927 $ 9,770 Non-cash financing activities: Mortgage notes assumed (1) $ 89,733 $ 146,000 Unrealized gain on interest rate derivatives $ 7,422 $ 768 _________________ (1) The approximately $89.7 million mortgage notes assumed during the six months ended June 30, 2018 , includes approximately $44.9 million of debt assumed when we acquired the remaining 50.00% interest in our Domain 8 property, and approximately $44.9 million of debt associated with our previously held 50.00% unconsolidated interest in the Domain 8 property. Domain 8 was consolidated during the six months ended June 30, 2018 . The approximately $146.0 million mortgage notes assumed during the six months ended June 30, 2017 , includes approximately $66.0 million of debt assumed when we acquired Legacy Union One, approximately $40.1 million of debt assumed when we acquired the remaining 50.16% interest in our Domain 2 and Domain 7 properties, and approximately $39.9 million of debt associated with our previously held 49.84% unconsolidated interest in the Domain 2 and Domain 7 properties. Domain 2 and Domain 7 were consolidated during the six months ended June 30, 2017 .

Basis of Presentation and Sig22

Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Real Estate	We amortize the value of in-place leases, in-place tenant improvements, and in-place leasing commissions to expense over the initial term of the respective leases. The tenant relationship values are amortized to expense over the tenants’ respective initial lease terms and any anticipated renewal periods, but in no event does the amortization period for intangible assets or liabilities exceed the remaining depreciable life of the building. Should a tenant terminate its lease, the unamortized portion of the acquired lease intangibles related to that tenant would be charged to expense. The estimated remaining average useful lives for acquired lease intangibles range from an ending date of July 2018 to an ending date of November 2027.
Hurricane Harvey	Hurricane Harvey In August 2017, One & Two Eldridge Place and Three Eldridge Place (collectively known as the “Eldridge Properties”), located in Houston, Texas, experienced flood-related damage as a result of Hurricane Harvey and its aftermath. By early January 2018, all of the properties were fully operational. We carry comprehensive property, casualty, flood, and business interruption insurance that we anticipate will cover our losses at the properties, subject to a deductible. In the third quarter of 2017, we recognized approximately $15.0 million for the write-off of the net book value of damaged assets, and we have incurred approximately $11.4 million of restoration expenses from August 2017 through June 2018. The write-off of the net book value of damaged assets and the restoration expenses incurred have been fully offset by an estimated insurance recovery. Since we determined receipt of insurance proceeds is probable, the estimated insurance recovery is recorded as a receivable and is included in “accounts receivable, net” on our condensed consolidated balance sheets. Through June 30, 2018 , we have received approximately $7.1 million of this insurance recovery. To the extent that insurance proceeds ultimately exceed the net book value of damaged assets plus the restoration expenses incurred, the excess (net of the deductible) will be reflected as income in the period insurance proceeds are received or when receipt is deemed probable to occur. During the three and six months ended June 30, 2018 , we provided rent abatements of approximately $0.8 million and $ 4.7 million , respectively, to tenants as a result of Hurricane Harvey. These abatements were a reduction to “rental revenue” on our condensed consolidated statements of operations and comprehensive income (loss) for the three and six months ended June 30, 2018 . For the three and six months ended June 30, 2018, these rent abatements were offset by approximately $0.4 million and $3.7 million , respectively, of business interruption insurance proceeds (net of estimated saved expenses). We anticipate we will receive remaining business interruption insurance proceeds in subsequent quarters.
Cash and Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents, and Restricted Cash We consider investments in highly-liquid money market funds or investments with original maturities of three months or less to be cash equivalents. Restricted cash includes restricted money market accounts, as required by our lenders or by leases, for anticipated tenant improvements, property taxes and insurance, certain tenant security deposits, and additional loan security reserves.
Accounts Receivable, net	Our allowance for doubtful accounts is an estimate based on management’s evaluation of accounts where it has determined that a tenant may not meet its financial obligations. In these situations, management uses its judgment, based on the facts and circumstances, and records a reserve for that tenant against amounts due to reduce the receivable to an amount it believes is collectible. These reserves are reevaluated and adjusted as additional information becomes available.
Investments in Unconsolidated Entities	Investments in Unconsolidated Entities Investments in unconsolidated entities consist of our noncontrolling interests in properties. We account for these investments using the equity method of accounting in accordance with GAAP. We use the equity method of accounting when we have significant influence, but not control, of the operating and financial decisions of these investments and thereby have some responsibility to create a return on our investment. The equity method of accounting requires these investments to be initially recorded at cost and subsequently increased (decreased) for our share of net income (loss), including eliminations for our share of inter-company transactions, and increased (decreased) for contributions (distributions). To the extent that we contribute assets to an unconsolidated entity, our investment in the unconsolidated entity is recorded at our cost basis in the assets that were contributed to the entity. To the extent that our cost basis is different than the basis reflected at the entity level, the basis difference is generally amortized over the life of the related asset and included in our share of equity in operations of investments. For unconsolidated investments that have properties under development, we capitalize interest expense to our investment basis using our weighted average interest rate of consolidated debt. Capitalization begins when we are engaged in the activities necessary to get the property ready for its intended use. We cease capitalization when the development is completed and ready for its intended use or if the intended use changes such that capitalization is no longer appropriate.
Noncontrolling Interests	Noncontrolling Interests Noncontrolling interests consists of our third-party partners’ proportionate share of equity in certain consolidated real estate properties and restricted stock units issued to our independent directors.
Revenue Recognition	Revenue Recognition Our rental revenue primarily consists of revenue generated from leases. We recognize rental income generated from all leases of consolidated real estate assets on a straight-line basis over the terms of the respective leases, including the effect of rent holidays, if any. For contracts with customers (as defined by GAAP), we recognize revenue when we transfer promised goods or services to a customer in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Our revenue from contracts with customers primarily consists of parking income, development fee income, and gain on sale of assets. Parking income - Parking income is primarily generated (1) through contractual arrangements with management companies that operate our parking garages and remit the monthly revenue collected to us or (2) directly through tenant leases. Revenue is recognized at a point in time upon the performance of services. Accounts receivable are recorded for services provided in advance of receiving payment. Management applies judgment in determining whether we are the principal or agent in those arrangements with management companies. We report revenue and expenses from these arrangements on a gross basis since we control the fulfillment of the promise to provide the service. Development fee income - We serve as a development manager for development projects owned by unconsolidated entities in which we have an ownership interest. Development fees are paid monthly and structured based on costs that approximate the percentage of construction completed. Our performance obligation is therefore satisfied over time, and we recognize development fee income based on progress of the developments. Gain on sale of assets - Upon the disposition of a property, we recognize a gain or loss at a point in time when we determine control of the underlying asset has been transferred to the buyer. Our performance obligation is generally satisfied at closing of the transaction. Any continuing involvement is analyzed as a separate performance obligation in the contract and a portion of the sales price is allocated to each performance obligation. When the performance obligation related to the continuing involvement is satisfied, the sales price allocated to it is recognized. There is significant judgment applied to estimate the amount of any variable consideration identified within the sales price and assess its probability of occurrence based on current market information, historical transactions, and forecasted information that is reasonably available.

Basis of Presentation and Sig23

Basis of Presentation and Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Schedule of cost basis, accumulated depreciation and amortization related to entity's consolidated real estate properties and related lease intangibles	The following is a summary of our buildings and improvements and related lease intangibles as of June 30, 2018 , and December 31, 2017 (in thousands): Lease Intangibles Assets Liabilities Acquired Above-Market Leases Acquired Below-Market Leases Buildings and Improvements Other Lease Intangibles as of June 30, 2018 Cost $ 1,642,748 $ 173,283 $ 4,857 $ (61,205 ) Less: accumulated depreciation and amortization (482,475 ) (67,405 ) (4,677 ) 35,295 Net $ 1,160,273 $ 105,878 $ 180 $ (25,910 ) Lease Intangibles Assets Liabilities Acquired Above-Market Leases Acquired Below-Market Leases Buildings and Improvements Other Lease Intangibles as of December 31, 2017 Cost $ 1,514,544 $ 146,926 $ 4,857 $ (50,399 ) Less: accumulated depreciation and amortization (453,126 ) (60,298 ) (4,438 ) 32,457 Net $ 1,061,418 $ 86,628 $ 419 $ (17,942 )
Anticipated amortization associated with the acquired lease intangibles for each of the five years	Anticipated amortization associated with acquired lease intangibles for each of the following five years is as follows (in thousands): July 2018 - December 2018 3,594 2019 7,119 2020 6,274 2021 5,025 2022 4,323
Cash, cash equivalents and restricted cash	The following is a summary of our total cash, cash equivalents, and restricted cash as presented in our statements of cash flows for the six months ended June 30, 2018 and 2017 (in thousands): June 30, June 30, Cash and cash equivalents $ 8,359 $ 28,763 Restricted cash 14,086 10,953 Total cash, cash equivalents, and restricted cash $ 22,445 $ 39,716
Cash, cash equivalents and restricted cash	The following is a summary of our total cash, cash equivalents, and restricted cash as presented in our statements of cash flows for the six months ended June 30, 2018 and 2017 (in thousands): June 30, June 30, Cash and cash equivalents $ 8,359 $ 28,763 Restricted cash 14,086 10,953 Total cash, cash equivalents, and restricted cash $ 22,445 $ 39,716
Summary of net accounts receivable	The following is a summary of our accounts receivable as of June 30, 2018 , and December 31, 2017 (in thousands): June 30, December 31, Straight-line rental revenue receivable $ 53,674 $ 57,372 Insurance receivable 19,717 18,826 Tenant receivables 6,217 4,221 Non-tenant receivables 1,564 893 Allowance for doubtful accounts (417 ) (183 ) Total $ 80,755 $ 81,129

Real Estate Activities (Tables)

Real Estate Activities (Tables)	6 Months Ended
	Jun. 30, 2018
Real Estate Activities [Abstract]
Sale of Real Estate	The following table presents our sales of real estate for the six months ended June 30, 2018 (in thousands): Property Name Date of Sale Location Rentable Square Footage Contract Sale Price Proceeds from Sale 500 East Pratt 02/13/18 Baltimore, MD 280 $ 60,000 $ 56,528 Centreport Office Center 02/22/18 Fort Worth, TX 133 12,696 12,421 Loop Central 03/27/18 Houston, TX 575 72,982 71,978 988 $ 145,678 $ 140,927
Schedule of assets and liabilities associated with real estate held for sale	The major classes of assets and obligations associated with real estate held for sale as of December 31, 2017, were as follows (in thousands): December 31, 2017 Buildings and improvements, net of approximately $29.0 million in accumulated depreciation $ 45,396 Accounts receivable and other assets 3,335 Lease intangibles, net of approximately $5.6 million in accumulated amortization 2,830 Other intangible assets, net of approximately $1.2 million in accumulated amortization 1,787 Assets associated with real estate held for sale $ 53,348 Acquired below-market leases, net of approximately $1.3 million in accumulated amortization $ 364 Other liabilities 1,990 Obligations associated with real estate held for sale $ 2,354

Investments in Unconsolidated25

Investments in Unconsolidated Entities (Tables)	6 Months Ended
	Jun. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Summary of the entity's investments in unconsolidated entities	The following is a summary of our investments in unconsolidated entities as of June 30, 2018 , and December 31, 2017 (dollar amounts in thousands): Ownership Interest Unconsolidated Investment Balance Entity Name Property June 30, December 31, 2017 June 30, December 31, Domain Junction 8 Venture LLC (1)(2) Domain 8 100.00 % 50.00 % $ — $ 882 208 Nueces Street, LLC (2) Third + Shoal 47.50 % 47.50 % 31,714 30,970 Total (3) ` $ 31,714 $ 31,852 _________________ (1) On March 30, 2018, we acquired the unrelated third party’s 50% interest in Domain Junction 8 Venture LLC increasing our ownership interest to 100% , and this property was consolidated. (2) We evaluate our investments in unconsolidated entities in order to determine if they are variable interest entities (“VIEs”). Based on our assessment, we identified each of these entities as a VIE, but we are not the primary beneficiary, as we do not have the power to direct the activities that most significantly impact the economic performance of these entities. For VIEs in which we are not deemed to be the primary beneficiary, we continue to account for them using the equity method. The maximum amount of exposure to loss with respect to these VIEs is the carrying amount of our investment and any debt guaranteed by us. As of June 30, 2018 , and December 31, 2017 , Tier OP guaranteed 25% and 50% , respectively, of the construction loan of 208 Nueces Street, LLC, as discussed below in “Guarantees.” At June 30, 2018 , our VIEs have total assets of approximately $108.8 million and total liabilities of approximately $54.3 million . At December 31, 2017 , our VIEs had total assets of approximately $172.3 million and total liabilities of approximately $125.1 million . (3) Our investments in unconsolidated entities at June 30, 2018 , and December 31, 2017 , include basis adjustments that total approximately $5.8 million and $9.4 million , respectively. These amounts represent the aggregate difference between our historical cost basis and our equity basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differences occur from impairment of investments and upon the transfer of assets that were previously owned by us into a joint venture. In addition, capitalized interest and certain acquisition, transaction, and other costs may not be reflected in the net assets at the joint venture level.

Notes Payable, net (Tables)

Notes Payable, net (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Schedule of long-term debt maturities	The following table provides information regarding the timing of principal payments of our notes payable, net, as of June 30, 2018 (in thousands): Principal payments due in: July 2018 - December 2018 $ 48,917 2019 1,589 2020 91,403 2021 72,402 2022 308,000 Thereafter 366,000 Less: unamortized debt issuance costs (1) (2,051 ) Notes payable, net $ 886,260 ________________ (1) Excludes approximately $3.2 million of unamortized debt issuance costs associated with the revolving line of credit because these costs are presented as an asset on our condensed consolidated balance sheets.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of financial assets and liabilities measured at fair value on a recurring basis	The following table sets forth our financial assets and liabilities measured at fair value on a recurring basis, which equals book value, by level within the fair value hierarchy as of June 30, 2018 , and December 31, 2017 (in thousands): Basis of Fair Value Measurements Quoted Prices In Active Markets for Identical Items (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Description June 30, 2018 Derivative financial instruments: Assets $ 12,467 $ — $ 12,467 $ — December 31, 2017 Derivative financial instruments: Assets $ 5,045 $ — $ 5,045 $ —
Schedule of carrying amounts and related estimated fair value of notes payable	Carrying amounts of our notes payable and the related estimated fair value as of June 30, 2018 , and December 31, 2017 , are as follows (in thousands): June 30, 2018 December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value Notes payable $ 888,311 $ 891,216 $ 801,339 $ 805,786 Less: unamortized debt issuance costs (2,051 ) (6,801 ) Notes payable, net $ 886,260 $ 794,538

Derivative Instruments and He28

Derivative Instruments and Hedging Activities (Tables)	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	The following table summarizes the notional values of our derivative financial instruments (in thousands) as of June 30, 2018 . The notional values provide an indication of the extent of our involvement in these instruments at June 30, 2018 , but do not represent exposure to credit, interest rate, or market risks. Type/Description Notional Value Index Strike Rate Effective Date Maturity Date Interest rate swap - cash flow hedge $ 125,000 one-month LIBOR 1.6775 % 12/31/14 10/31/19 Interest rate swap - cash flow hedge $ 125,000 one-month LIBOR 1.6935 % 04/30/15 10/31/19 Interest rate swap - cash flow hedge $ 125,000 one-month LIBOR 1.7615 % 06/30/15 05/31/22 Interest rate swap - cash flow hedge $ 150,000 one-month LIBOR 1.7695 % 06/30/15 05/31/22
Schedule of fair value of derivative financial instruments included in other liabilities	The table below presents the fair value of our derivative financial instruments, included in “prepaid expenses and other assets” on our condensed consolidated balance sheets, as of June 30, 2018 , and December 31, 2017 (in thousands): Derivatives Designated as Hedging Instruments: Derivative Assets June 30, December 31, Interest rate swaps $ 12,467 $ 5,045
Schedule of effect of the change in fair value of derivative financial instruments in statement of operations and comprehensive income (loss)	The tables below present the effect of the change in fair value of derivative financial instruments in our condensed consolidated statements of operations and comprehensive income (loss) for the three and six months ended June 30, 2018 and 2017 (in thousands): Derivatives in Cash Flow Hedging Relationship Gain (loss) recognized in OCI on derivatives Three Months Ended Six Months Ended June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Interest rate swaps $ 1,984 $ (1,301 ) $ 7,422 $ 768 Amount reclassified from OCI into income Three Months Ended Six Months Ended Location June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Interest expense (1) $ (259 ) $ 953 $ (100 ) $ 2,199 ______________ (1) Increases (decreases) in fair value as a result of accrued interest associated with our swap transactions are recorded in accumulated OCI and subsequently reclassified into income. Such amounts are shown net in the condensed consolidated statements of changes in equity and offset dollar for dollar. Total interest expense presented in the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) in which the effects of cash flow hedges are recorded Three Months Ended Six Months Ended Location June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Interest expense $ 8,369 $ 8,235 $ 16,478 $ 17,015

Equity (Tables)

Equity (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Schedule of Restricted Stock Units	The following is a summary of the number of outstanding RSUs held by our employees as of June 30, 2018 and 2017 : June 30, 2018 June 30, 2017 Units Weighted Average Price per unit Units Weighted Average Price per unit Outstanding at the beginning of the year 208,620 $ 16.59 111,063 $ 15.26 Issued 129,188 $ 17.24 97,557 $ 18.10 Outstanding at the end of the period 337,808 $ 16.84 208,620 $ 16.59 The following is a summary of the number of outstanding RSUs held by our independent directors as of June 30, 2018 and 2017 : June 30, 2018 June 30, 2017 Units Weighted Average Price per unit Units Weighted Average Price per unit Outstanding at the beginning of the year 19,672 $ 17.03 39,255 $ 16.45 Issued 12,910 $ 23.24 19,672 $ 17.03 Converted (19,672 ) $ 17.03 (29,307 ) $ 16.92 Outstanding at the end of the period (1) 12,910 $ 23.24 29,620 $ 16.38 _____________ (1) As of June 30, 2018 , none of the RSUs held by our independent directors are vested.
Summary of Restricted Stock Valuation Assumptions	Compensation cost is measured at the grant date, based on the estimated fair value of the award (ranging from $16.80 per unit to $20.95 per unit) as determined by a Monte Carlo simulation-based model using the assumptions outlined in the table below. Any forfeitures of awards are recognized as they occur. Assumption Value Expected volatility 24% - 26% Risk-free interest rate 1.15% - 2.37% Expected term 35 months Expected dividend yield 3.7% - 4.5%
Summary of the Number of Shares of Restricted Stock Outstanding	The following is a summary of the number of shares of restricted stock outstanding as of June 30, 2018 and 2017 : June 30, 2018 June 30, 2017 Shares Weighted Average Price per share Shares Weighted Average Price per share Outstanding at the beginning of the year 180,791 $ 20.47 246,805 $ 20.74 Issued 125,558 $ 17.24 121,860 $ 17.88 Forfeitures (4,914 ) $ 17.10 (20,089 ) $ 17.53 Restrictions lapsed (41,062 ) $ 26.23 (57,553 ) $ 25.64 Outstanding at the end of the period 260,373 $ 18.07 291,023 $ 18.79

Net Income (Loss) per Common 30

Net Income (Loss) per Common Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Basic and diluted net income per common share	The following table reflects the calculation of basic and diluted net income (loss) per common share for the three and six months ended June 30, 2018 and 2017 (in thousands, except per share data): Three Months Ended Six Months Ended June 30, 2018 June 30, 2017 June 30, 2018 June 30, 2017 Numerator: Net income (loss) attributable to common stockholders $ (8,277 ) $ 4,031 $ 113 $ 102,202 Less: net income allocated to participating securities — — — (611 ) Numerator for basic net income (loss) per share $ (8,277 ) $ 4,031 $ 113 $ 101,591 Add: undistributed net income allocated to participating securities — — — 506 Less: undistributed net income re-allocated to participating securities — — — (504 ) Numerator for diluted net income (loss) per share (1) $ (8,277 ) $ 4,031 $ 113 $ 101,593 Denominator: Weighted average common shares outstanding - basic 47,684 47,536 47,665 47,524 Effect of dilutive securities — 339 812 204 Weighted average common shares outstanding - diluted 47,684 47,875 48,477 47,728 Basic net income (loss) per common share $ (0.17 ) $ 0.08 $ 0.00 $ 2.14 Diluted net income (loss) per common share $ (0.17 ) $ 0.08 $ 0.00 $ 2.13 Securities excluded from weighted average common shares outstanding-diluted because their effect would be anti-dilutive 992 29 17 29 _______________ (1) In periods where there is no undistributed net income to allocate to participating securities, the treasury stock method is used to calculate dilutive securities.

Supplemental Cash Flow Inform31

Supplemental Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flow information	Supplemental cash flow information is summarized below for the six months ended June 30, 2018 and 2017 (in thousands): Six Months Ended June 30, 2018 June 30, 2017 Interest paid, net of amounts capitalized $ 14,211 $ 12,695 Income taxes paid $ 758 $ 403 Non-cash investing activities: Property and equipment additions in accounts payable and accrued liabilities $ 17,382 $ 7,816 Liabilities assumed through the purchase of real estate $ 7,028 $ 3,267 Escrow deposits applied to purchase of real estate $ 21,350 $ 14,000 Escrow deposit applied to purchase of real estate from noncontrolling interest $ 150 $ — Sale of real estate and lease intangibles to unconsolidated joint venture $ — $ 13,804 Acquisition of controlling interest in unconsolidated entity $ 927 $ 9,770 Non-cash financing activities: Mortgage notes assumed (1) $ 89,733 $ 146,000 Unrealized gain on interest rate derivatives $ 7,422 $ 768 _________________ (1) The approximately $89.7 million mortgage notes assumed during the six months ended June 30, 2018 , includes approximately $44.9 million of debt assumed when we acquired the remaining 50.00% interest in our Domain 8 property, and approximately $44.9 million of debt associated with our previously held 50.00% unconsolidated interest in the Domain 8 property. Domain 8 was consolidated during the six months ended June 30, 2018 . The approximately $146.0 million mortgage notes assumed during the six months ended June 30, 2017 , includes approximately $66.0 million of debt assumed when we acquired Legacy Union One, approximately $40.1 million of debt assumed when we acquired the remaining 50.16% interest in our Domain 2 and Domain 7 properties, and approximately $39.9 million of debt associated with our previously held 49.84% unconsolidated interest in the Domain 2 and Domain 7 properties. Domain 2 and Domain 7 were consolidated during the six months ended June 30, 2017 .

Business (Details)

Business (Details)	Jun. 30, 2018propertymarket
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating office properties	18
Number of non-operating properties	1
Number of development properties	3
Number of markets in which the entity operates interests in properties | market	6

Basis of Presentation and Sig33

Basis of Presentation and Significant Accounting Policies (Real Estate) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Real estate properties
Net	$ 1,160,273	$ 1,061,418
Intangible assets
Net	106,058	87,047
Intangible liabilities
Net	(25,910)	(17,942)
Other Lease Intangibles
Intangible assets
Cost	173,283	146,926
Less: accumulated depreciation and amortization	(67,405)	(60,298)
Net	105,878	86,628
Acquired Above-Market Leases
Intangible assets
Cost	4,857	4,857
Less: accumulated depreciation and amortization	(4,677)	(4,438)
Net	180	419
Acquired Below-Market Leases
Intangible liabilities
Cost	(61,205)	(50,399)
Less: accumulated depreciation and amortization	35,295	32,457
Net	(25,910)	(17,942)
Anticipated amortization associated with acquired lease intangibles
Anticipated Amortization Associated with the Acquired Lease Intangibles for Each of the Following Five Years
July 2018 - December 2018	3,594
2,019	7,119
2,020	6,274
2,021	5,025
2,022	4,323
Buildings and Improvements
Real estate properties
Cost	1,642,748	1,514,544
Less: accumulated depreciation and amortization	(482,475)	(453,126)
Net	$ 1,160,273	$ 1,061,418

Basis of Presentation and Sig34

Basis of Presentation and Significant Accounting Policies (Hurricane Harvey) (Details) - Hurricane - USD ($) $ in Millions	3 Months Ended	6 Months Ended	11 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2018	Sep. 30, 2017
Unusual or Infrequent Item, or Both [Line Items]
Write-off net book value of damaged assets				$ 15
Restoration costs			$ 11.4
Estimated insurance recoveries			$ 7.1
Business interruption loss
Unusual or Infrequent Item, or Both [Line Items]
Hurricane related costs, rent abatements	$ 0.8	$ 4.7
Hurricane related costs, insurance proceeds (net of estimated saved expenses)	$ 0.4	$ 3.7

Basis of Presentation and Sig35

Basis of Presentation and Significant Accounting Policies (Cash, Cash Equivalents, and Restricted Cash) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 8,359	$ 13,800	$ 28,763
Restricted cash	14,086	8,510	10,953
Total cash, cash equivalents, and restricted cash	$ 22,445	$ 22,310	$ 39,716	$ 22,393

Basis of Presentation and Sig36

Basis of Presentation and Significant Accounting Policies (Accounts Receivable, net) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts Receivable, Net [Abstract]
Straight-line rental revenue receivable	$ 53,674	$ 57,372
Insurance receivable	19,717	18,826
Tenant receivables	6,217	4,221
Non-tenant receivables	1,564	893
Allowance for doubtful accounts	(417)	(183)
Total	$ 80,755	$ 81,129

Basis of Presentation and Sig37

Basis of Presentation and Significant Accounting Policies (Investments in Unconsolidated Entities) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Investments in Unconsolidated Entities [Line Items]
Interest costs capitalized	$ 1.8	$ 0.6
Unconsolidated Entity
Investments in Unconsolidated Entities [Line Items]
Interest costs capitalized	$ 0.6	$ 0.7

New Accounting Pronouncements -

New Accounting Pronouncements - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect adjustment			$ 1,460
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Extinguishment of debt, amount	$ 400
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect adjustment			635	$ (290)
Retained earnings | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect adjustment		$ (1,500)
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect adjustment			$ 825
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2017-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect adjustment		$ 800

Real Estate Activities (Sales o

Real Estate Activities (Sales of Real Estate) (Details) ft² in Thousands, $ in Thousands	Mar. 27, 2018USD ($)ft²	Feb. 22, 2018USD ($)ft²	Feb. 13, 2018USD ($)ft²	Jun. 30, 2018USD ($)ft²	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)ft²	Jun. 30, 2017USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale						$ 141,149	$ 330,045
Contributed net income				$ 100	$ 1,800	$ 800	$ 3,500
500 East Pratt
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable square feet | ft²			280
Contract sale price			$ 60,000
Proceeds from sale			$ 56,528
Centreport Office Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable square feet | ft²		133
Contract sale price		$ 12,696
Proceeds from sale		$ 12,421
Loop Central
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable square feet | ft²	575
Contract sale price	$ 72,982
Proceeds from sale	$ 71,978
500 East Pratt, Centreport Office Center, and Loop Central [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable square feet | ft²				988		988
Contract sale price				$ 145,678		$ 145,678
Proceeds from sale						$ 140,927

Real Estate Activities (Acquisi

Real Estate Activities (Acquisitions of Real Estate) (Details) ft² in Thousands, $ in Thousands	Mar. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2018	Mar. 29, 2018	Jan. 05, 2018	Jan. 04, 2018USD ($)ft²building	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Lease intangibles, net		$ 106,058		$ 106,058						$ 87,047
Acquired below-market leases, net		25,910		25,910						$ 17,942
Gain (loss) on remeasurement of investment in unconsolidated entities		$ (152)	$ 0	$ 11,090	$ 14,168
Domain Point
Business Acquisition [Line Items]
Ownership Interest								100.00%	96.50%
Contract purchase price									$ 73,800
Number of buildings | building									2
Rentable square feet | ft²									240
Lease intangibles, net									$ 9,300
Acquired below-market leases, net									$ 2,800
Domain Point, Owner
Business Acquisition [Line Items]
Ownership Interest									90.00%
Domain 8
Business Acquisition [Line Items]
Ownership Interest	50.00%	100.00%		100.00%		100.00%	50.00%			50.00%
Contract purchase price	$ 92,800
Lease intangibles, net	21,300
Acquired below-market leases, net	8,300
Acquisition, debt assumed	44,900			$ 44,900
Gain (loss) on remeasurement of investment in unconsolidated entities	$ 11,100

Real Estate Activities (Real Es

Real Estate Activities (Real Estate Held for Sale) (Details) $ in Thousands	Jun. 30, 2018USD ($)property	Dec. 31, 2017USD ($)
Long lived assets held for sale [Abstract]
Buildings and improvements, net	$ 1,160,273	$ 1,061,418
Lease intangibles, net	106,058	87,047
Assets associated with real estate held for sale	0	53,348
Acquired below-market leases, net	25,910	17,942
Obligations associated with real estate held for sale	$ 0	2,354
Assets held-for-sale
Real Estate Properties [Line Items]
Number of operating office properties | property	0
Long lived assets held for sale [Abstract]
Buildings and improvements, net		45,396
Accumulated depreciation, buildings and improvements		(29,000)
Accounts receivable and other assets		3,335
Lease intangibles, net		2,830
Accumulated amortization, lease intangibles		(5,600)
Other intangible assets, net		1,787
Accumulated amortization, other intangible assets		(1,200)
Assets associated with real estate held for sale		53,348
Acquired below-market leases, net		364
Accumulated amortization, acquired below-market leases		(1,300)
Other liabilities		1,990
Obligations associated with real estate held for sale		$ 2,354

Real Estate Under Development (

Real Estate Under Development (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Real Estate Under Development [Abstract]
Development costs capitalized	$ 43.4	$ 8.9
Interest costs capitalized	$ 1.8	$ 0.6

Investments in Unconsolidated43

Investments in Unconsolidated Entities (Summary of Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Mar. 31, 2018	Mar. 30, 2018	Mar. 29, 2018
Investments in Unconsolidated Entities [Line Items]
Unconsolidated Investment Balance	$ 31,714		$ 31,714		$ 31,852
Equity method investment, basis adjustment	5,800		5,800		$ 9,400
Equity in operations of investments	$ 0	$ 6,556	$ 287	$ 6,300
Domain 8
Investments in Unconsolidated Entities [Line Items]
Ownership Interest	100.00%		100.00%		50.00%	100.00%	50.00%	50.00%
Unconsolidated Investment Balance	$ 0		$ 0		$ 882
Third Shoal
Investments in Unconsolidated Entities [Line Items]
Ownership Interest	47.50%		47.50%		47.50%
Unconsolidated Investment Balance	$ 31,714		$ 31,714		$ 30,970
Domain 8 and Third and Shoal
Investments in Unconsolidated Entities [Line Items]
Unconsolidated Investment Balance	31,714		31,714		31,852
1325 G Street and Colorado Building
Investments in Unconsolidated Entities [Line Items]
Equity in operations of investments					6,700
Variable Interest Entity, not primary beneficiary
Investments in Unconsolidated Entities [Line Items]
Total assets	108,800		108,800		172,300
Total liabilities	54,300		$ 54,300		$ 125,100
TIER Operating Partnership | Third Shoal
Investments in Unconsolidated Entities [Line Items]
Loan guarantee, percentage			25.00%		50.00%
Debt obligation | TIER Operating Partnership | Third Shoal
Investments in Unconsolidated Entities [Line Items]
Obligation, commitment	103,800		$ 103,800
Obligation, maximum exposure	26,000		26,000
Construction loan guarantee | TIER Operating Partnership | Third Shoal
Investments in Unconsolidated Entities [Line Items]
Obligation, commitment	44,700		44,700
Obligation, maximum exposure	$ 11,200		$ 11,200

Notes Payable, net (Narrative)

Notes Payable, net (Narrative) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Notes payable, net	$ 886,260,000	$ 794,538,000
Notes payable, net secured by real estate assets	279,200,000
Carrying value of real estate securing notes payable	$ 398,800,000
Default interest rate	5.00%
Increase in interest expense for loans that are in default	$ 1,200,000
Line of credit, maximum borrowing capacity	$ 900,000,000
Revolving loan extension period	1 year
LIBOR interest index period one	1 month
LIBOR interest index period two	3 months
LIBOR Interest Index period three	6 months
Amount of borrowings with risk managed by hedged interest rates	$ 525,000,000
Available additional borrowings	$ 209,400,000
Weighted average interest rate for borrowings under the credit facility	3.46%
Federal Funds Effective Rate | Line of credit
Line of Credit Facility [Line Items]
Applicable margin	0.50%
Debt Instrument Variable Rate Base Libor | Line of credit
Line of Credit Facility [Line Items]
Applicable margin	1.00%
Term loan facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	$ 300,000,000
Second term loan facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	275,000,000
Revolving credit facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	325,000,000
Borrowings outstanding	33,000,000
Term loan facility and second term loan facility
Line of Credit Facility [Line Items]
Borrowings outstanding	575,000,000
Fifth Third Center - Columbus OH
Line of Credit Facility [Line Items]
Carrying value of real estate securing notes payable	31,600,000
Outstanding balance of non-recourse property loan in default	$ 48,200,000
Minimum
Line of Credit Facility [Line Items]
Line of credit, applicable margin	0.10%
Maximum
Line of Credit Facility [Line Items]
Line of credit, applicable margin	2.35%
Notes payable
Line of Credit Facility [Line Items]
Notes payable, net	$ 886,260,000
Debt bearing interest at variable rates	$ 172,700,000
Weighted average interest rate for consolidated debt	3.91%
Effective average interest rate with loan in default	4.19%
Notes payable | Minimum
Line of Credit Facility [Line Items]
Stated annual interest rate	3.16%
Notes payable | Maximum
Line of Credit Facility [Line Items]
Stated annual interest rate	6.09%

Notes Payable, net (Schedule of

Notes Payable, net (Schedule of Long-Term Debt Maturities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Principal payments due in:
Notes payable, net	$ 886,260	$ 794,538
Deferred financing fees, net	3,211	$ 1,387
Notes payable
Principal payments due in:
July 2018 - December 2018	48,917
2,019	1,589
2,020	91,403
2,021	72,402
2,022	308,000
Thereafter	366,000
Less: unamortized debt issuance costs	(2,051)
Notes payable, net	886,260
Revolving credit facility
Principal payments due in:
Deferred financing fees, net	$ 3,200

Fair Value Measurements (Financ

Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - Total Fair Value - Recurring basis - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 12,467	$ 5,045
Quoted Prices In Active Markets for Identical Items (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	12,467	5,045
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 0	$ 0

Fair Value Measurements (Fina47

Fair Value Measurements (Financial Instruments not Reported at Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable, net	$ 886,260	$ 794,538
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable	888,311	801,339
Less: unamortized debt issuance costs	(2,051)	(6,801)
Notes payable, net	886,260	794,538
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable	$ 891,216	$ 805,786

Derivative Instruments and He48

Derivative Instruments and Hedging Activities (Notional Values of Derivative Financial Instruments) (Details)	Jun. 30, 2018USD ($)
Derivative [Line Items]
Notional Value	$ 525,000,000
Swap Number One
Derivative [Line Items]
Notional Value	$ 125,000,000
Strike Rate	1.6775%
Swap Number Two
Derivative [Line Items]
Notional Value	$ 125,000,000
Strike Rate	1.6935%
Swap Number Three
Derivative [Line Items]
Notional Value	$ 125,000,000
Strike Rate	1.7615%
Swap Number Four
Derivative [Line Items]
Notional Value	$ 150,000,000
Strike Rate	1.7695%

Derivative Instruments and He49

Derivative Instruments and Hedging Activities (Fair Value of Derivative Financial Instruments Included in Other Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Designated as hedging instrument | Interest rate swaps
Derivative [Line Items]
Derivative Assets	$ 12,467	$ 5,045

Derivative Instruments and He50

Derivative Instruments and Hedging Activities (Derivatives in Cash Flow Hedging Relationship) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ 8,369	$ 8,235	$ 16,478	$ 17,015
Cash flow hedging | Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from OCI into income	(259)	953	(100)	2,199
Total interest expense presented in the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) in which the effects of cash flow hedges are recorded	8,369	8,235	16,478	17,015
Cash flow hedging | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in OCI on derivatives	$ 1,984	$ (1,301)	$ 7,422	$ 768

Derivative Instruments and He51

Derivative Instruments and Hedging Activities (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)
Debt Instrument, by Type [Line Items]
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net	$ 3.5
Period over which default must be remedied	30 days
Recourse debt
Debt Instrument, by Type [Line Items]
Minimum amount of debt default that could cause derivative obligations to also be in default	$ 10
Non-recourse debt
Debt Instrument, by Type [Line Items]
Minimum amount of debt default that could cause derivative obligations to also be in default	$ 75

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)executive
Commitments for future tenant improvements and leasing commissions
Commitments and contingencies
Future tenant improvements and leasing commissions	$ 17.2
Employment agreements
Commitments and contingencies
Number of executives | executive	5
Period of automatic continuation of term of employment	1 year
Notice period for non-renewal of term prior to the expiration of the initial term	60 days
Compensation expense if termination of employment without cause	$ 14.3

Equity (Restricted Stock Units)

Equity (Restricted Stock Units) (Details)	6 Months Ended		25 Months Ended
	Jun. 30, 2018Metric$ / sharesshares	Jun. 30, 2017Metric$ / sharesshares	Dec. 31, 2020
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted stock units held by independent directors, vested (in units) | shares	0
Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, vesting period	13 months
Directors | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at the beginning of the year (in shares/units) | shares	19,672	39,255
Issued (in units) | shares	12,910	19,672
Converted (in units) | shares	(19,672)	(29,307)
Outstanding at the end of the year (in shares/units) | shares	12,910	29,620
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted average price per unit, outstanding at the beginning of the year (in dollars per share/unit)	$ 17.03	$ 16.45
Weighted average price per unit, issued (in dollars per unit)	23.24	17.03
Weighted average price per unit, converted (in dollars per unit)	17.03	16.92
Weighted average price per unit, outstanding at the end of the year (in dollars per share/unit)	$ 23.24	$ 16.38
Employee | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at the beginning of the year (in shares/units) | shares	208,620	111,063
Issued (in units) | shares	129,188	97,557
Outstanding at the end of the year (in shares/units) | shares	337,808	208,620
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted average price per unit, outstanding at the beginning of the year (in dollars per share/unit)	$ 16.59	$ 15.26
Weighted average price per unit, issued (in dollars per unit)	17.24	18.10
Weighted average price per unit, outstanding at the end of the year (in dollars per share/unit)	$ 16.84	$ 16.59
Number of metrics used to compare annualized total stockholder return to | Metric	3	3
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected term	35 months	35 months
Employee | Restricted Stock Units (RSUs) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Estimated fair value of award determined by Monte Carlo model (in dollars per unit)	$ 16.80
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	24.00%	24.00%
Risk-free interest rate	1.15%	1.15%
Expected dividend yield	3.70%	3.70%
Employee | Restricted Stock Units (RSUs) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Estimated fair value of award determined by Monte Carlo model (in dollars per unit)	$ 20.95
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	26.00%	26.00%
Risk-free interest rate	2.37%	2.37%
Expected dividend yield	4.50%	4.50%
Employee | Restricted Stock Units (RSUs) | Scenario, forecast | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of common stock shares that restricted stock units can be converted to (in percent)			0.00%
Employee | Restricted Stock Units (RSUs) | Scenario, forecast | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of common stock shares that restricted stock units can be converted to (in percent)			200.00%

Equity (Restricted Stock) (Deta

Equity (Restricted Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Compensation expense related to the amortization of all equity-based incentive awards	$ 1.2	$ 1	$ 2.2	$ 1.9
Total remaining compensation cost on unvested awards	$ 5.9		$ 5.9
Compensation cost not yet recognized, unvested awards, period for recognition			1 year 5 months
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at the beginning of the year (in shares/units)			180,791	246,805
Issued (in shares)			125,558	121,860
Forfeiture (in shares)			(4,914)	(20,089)
Restrictions lapsed (in units)			(41,062)	(57,553)
Outstanding at the end of the year (in shares/units)	260,373	291,023	260,373	291,023
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted average price per unit, outstanding at the beginning of the year (in dollars per share/unit)			$ 20.47	$ 20.74
Weighted average price per unit, issues (in dollars per share)			17.24	17.88
Weighted average price per unit, forfeited (in dollars per share)			17.10	17.53
Weighted average price per unit, restrictions lapsed (in dollars per share)			26.23	25.64
Weighted average price per unit, outstanding at the end of the year (in dollars per share/unit)	$ 18.07	$ 18.79	$ 18.07	$ 18.79

Equity (ATM Program) (Details)

Equity (ATM Program) (Details) - USD ($)	Jul. 01, 2018	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	May 10, 2017
Class of Stock [Line Items]
Common stock, shares issued (shares)		48,574,724	48,574,724		47,623,324
Issuance of common stock, value			$ 21,302,000	$ 0
Issuance of common stock, issuance costs			$ 431,000	$ 0
ATM Program
Class of Stock [Line Items]
Common stock, authorized, value						$ 125,000,000
Common stock, shares issued (shares)		901,300	901,300
Issuance of common stock, value		$ 20,900,000
Issuance of common stock, commissions		300,000
Issuance of common stock, issuance costs		$ 100,000
ATM Program | Subsequent Event
Class of Stock [Line Items]
Common stock, shares issued (shares)	1,940,251
Issuance of common stock, value	$ 44,800,000
Issuance of common stock, commissions	600,000
Issuance of common stock, issuance costs	$ 200,000

Revenue - Rental Income (Detail

Revenue - Rental Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rental revenue	$ 53,990	$ 54,552	$ 108,133	$ 110,915
Straight-line rent adjustments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rental revenue	800	2,000	1,300	3,800
Deferred rent
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rental revenue	400	400	800	1,000
Acquired above- and below- market leases
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rental revenue	1,700	900	2,900	1,800
Lease termination fees
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rental revenue	$ 400	$ 100	$ 700	$ 200

Revenue - Revenue form Contract

Revenue - Revenue form Contracts with Customers (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer, gain (loss) on sale of assets	$ (100,000)	$ 1,300,000	$ 11,900,000	$ 92,000,000
Accounts receivable
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, contracts with customers	900,000		900,000		$ 600,000
Parking
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contracts with customers	2,300,000	2,000,000	4,600,000	3,900,000
Development fee
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contracts with customers	$ 0	$ 200,000	$ 0	$ 200,000

Net Income (Loss) per Common 58

Net Income (Loss) per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income (loss) attributable to common stockholders	$ (8,277)	$ 4,031	$ 113	$ 102,202
Less: net income allocated to participating securities	0	0	0	(611)
Numerator for basic net income (loss) per share	(8,277)	4,031	113	101,591
Add: undistributed net income allocated to participating securities	0	0	0	506
Less: undistributed net income re-allocated to participating securities	0	0	0	(504)
Numerator for diluted net income (loss) per share (1)	$ (8,277)	$ 4,031	$ 113	$ 101,593
Denominator:
Weighted average common shares outstanding - basic (in shares)	47,684,152	47,536,320	47,664,709	47,523,688
Effect of dilutive securities (in shares)	0	339,000	812,000	204,000
Weighted average common shares outstanding - diluted (in shares)	47,684,152	47,875,418	48,476,933	47,727,634
Basic income (loss) per common share (in dollars per share)	$ (0.17)	$ 0.08	$ 0	$ 2.14
Diluted income (loss) per common share (in dollars per share)	$ (0.17)	$ 0.08	$ 0	$ 2.13
Securities excluded from weighted average common shares outstanding-diluted because their effect would be anti-dilutive (in shares)	992,000	29,000	17,000	29,000

Supplemental Cash Flow Inform59

Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	Mar. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Mar. 29, 2018	Dec. 31, 2017	Jun. 29, 2017
Supplemental Cash Flow Elements [Abstract]
Interest paid, net of amounts capitalized		$ 14,211	$ 12,695
Income taxes paid		758	403
Non-cash investing activities:
Property and equipment additions in accounts payable and accrued liabilities		17,382	7,816
Liabilities assumed through the purchase of real estate		7,028	3,267
Escrow deposits applied to purchase of real estate		21,350	14,000
Escrow deposit applied to purchase of real estate from noncontrolling interest		150	0
Sale of real estate and lease intangibles to unconsolidated joint venture		0	13,804
Acquisition of controlling interest in unconsolidated entity		927	9,770
Non-cash financing activities:
Mortgage notes assumed (1)		89,733	146,000
Unrealized gain on interest rate derivatives		7,422	768
Domain 8
Non-cash financing activities:
Mortgage notes assumed (1)		89,700
Acquisition, debt assumed	$ 44,900	$ 44,900
Ownership Interest	50.00%	100.00%		100.00%	50.00%	50.00%
Domain 2 & Domain 7
Non-cash financing activities:
Mortgage notes assumed (1)			146,000
Acquisition, debt assumed			$ 40,100
Ownership Interest							49.84%
Ownership interest, acquired			50.16%
Real estate investment, debt			$ 39,900
Legacy Union One
Non-cash financing activities:
Mortgage notes assumed (1)			$ 66,000