Biomed Realty Trust 10-Q 29 Apr 15 2015 Q1 Quarterly report Financial data

Document_Entity_Information

Document Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 29, 2015
Entity Information [Line Items]
Entity Registrant Name	BioMed Realty Trust Inc
Entity Central Index Key	1289236
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		203,566,934
BIOMED REALTY, L.P.
Entity Information [Line Items]
Entity Registrant Name	BioMed Realty L P
Entity Central Index Key	1301932
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Investments in real estate, net	$5,517,629	$5,416,575
Investments in unconsolidated partnerships	34,978	35,291
Parent Company
Investments in real estate, net	5,517,629	5,416,575
Investments in unconsolidated partnerships	34,978	35,291
Cash and cash equivalents	64,958	46,659
Accounts receivable, net	13,518	14,631
Accrued straight-line rents, net	164,049	163,716
Deferred leasing costs, net	219,549	219,713
Other assets	293,737	274,301
Total assets	6,308,418	6,170,886
Liabilities [Abstract]
Mortgage notes payable, net	503,200	496,757
Exchangeable senior notes		95,678
Unsecured senior notes, net	1,294,255	1,293,903
Unsecured senior term loans	741,626	749,326
Unsecured line of credit	226,000	84,000
Accounts payable, accrued expenses and other liabilities	386,259	381,280
Total liabilities	3,151,340	3,100,944
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Common stock, $.01 par value, 250,000,000 shares authorized, 203,563,054 shares and 197,442,432 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	2,036	1,975
Additional paid-in capital	3,746,823	3,649,235
Accumulated other comprehensive loss, net	14,804	-2,214
Dividends in excess of earnings	-681,564	-645,983
Total stockholders' equity	3,082,099	3,003,013
Noncontrolling interests / Noncontrolling interests deficit	74,979	66,929
Total equity / capital	3,157,078	3,069,942
Total liabilities and equity / capital	6,308,418	6,170,886
BIOMED REALTY, L.P.
Investments in real estate, net	5,517,629	5,416,575
Investments in unconsolidated partnerships	34,978	35,291
Cash and cash equivalents	64,958	46,659
Accounts receivable, net	13,518	14,631
Accrued straight-line rents, net	164,049	163,716
Deferred leasing costs, net	219,549	219,713
Other assets	293,737	274,301
Total assets	6,308,418	6,170,886
Liabilities [Abstract]
Mortgage notes payable, net	503,200	496,757
Exchangeable senior notes		95,678
Unsecured senior notes, net	1,294,255	1,293,903
Unsecured senior term loans	741,626	749,326
Unsecured line of credit	226,000	84,000
Accounts payable, accrued expenses and other liabilities	386,259	381,280
Total liabilities	3,151,340	3,100,944
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Limited partners' capital, 5,405,474 issued and outstanding at March 31, 2015 and December 31, 2014, respectively	46,154	45,600
General partner's capital, 203,563,054 and 197,442,432 units issued and outstanding at March 31, 2015 and December 31, 2014, respectively	3,063,494	3,002,135
Accumulated other comprehensive loss, net	18,605	878
Total partners' capital	3,128,253	3,048,613
Noncontrolling interests / Noncontrolling interests deficit	28,825	21,329
Total equity / capital	3,157,078	3,069,942
Total liabilities and equity / capital	$6,308,418	$6,170,886

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Parent Company
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	250,000,000	250,000,000
Common Stock, Shares, Issued	203,563,054	197,442,432
BIOMED REALTY, L.P.
Limited Partners' Capital Account, Units Issued	5,405,474	5,405,474
Limited Partners' Capital Account, Units Outstanding	5,405,474	5,405,474
General Partners' Capital Account, Units Issued	203,563,054	197,442,432
General Partners' Capital Account, Units Outstanding	203,563,054	197,442,432
Common Stock | Parent Company
Common Stock, Shares Outstanding	203,563,054	197,442,432

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Expenses:
Equity in net loss of unconsolidated partnerships	$153	($138)
Parent Company
Revenues:
Rental	117,520	120,026
Tenant recoveries	43,956	38,735
Other revenue	16,534	10,115
Total revenues	178,010	168,876
Expenses:
Rental operations	58,647	52,523
Depreciation and amortization	67,080	62,409
General and administrative	12,789	11,942
Executive Severance	9,891	0
Acquisition-related expenses	464	1,250
Total expenses	148,871	128,124
Income from operations	29,139	40,752
Equity in net loss of unconsolidated partnerships	153	-138
Interest expense, net	-21,395	-28,010
Other expense	12,884	8,163
Net income / (loss)	20,781	20,767
Net (income) / loss attributable to noncontrolling interests	-3,436	-1,934
Net income / (loss) per share / unit available to common stockholders / unitholders	$0.08	$0.10
Weighted Average Number of Shares Outstanding, Basic	200,789,795	190,905,867
Weighted Average Number of Shares Outstanding, Diluted	206,536,148	196,545,536
Net Income (Loss) Attributable to Parent	17,345	18,833
BIOMED REALTY, L.P.
Revenues:
Rental	117,520	120,026
Tenant recoveries	43,956	38,735
Other revenue	16,534	10,115
Total revenues	178,010	168,876
Expenses:
Rental operations	58,647	52,523
Depreciation and amortization	67,080	62,409
General and administrative	12,789	11,942
Executive Severance	9,891	0
Acquisition-related expenses	464	1,250
Total expenses	148,871	128,124
Income from operations	29,139	40,752
Equity in net loss of unconsolidated partnerships	153	-138
Interest expense, net	-21,395	-28,010
Gain (Loss) on Sale of Properties	0
Other expense	12,884	8,163
Net income / (loss)	20,781	20,767
Net (income) / loss attributable to noncontrolling interests	-2,979	-1,413
Net Income (Loss) Allocated to Limited Partners	$17,802	$19,354
Net income / (loss) per share / unit available to common stockholders / unitholders	$0.08	$0.10
Earnings Per Share, Diluted	$0.08
Weighted Average Number of Shares Outstanding, Basic	206,195,269	196,316,241
Weighted Average Number of Shares Outstanding, Diluted	206,536,148	196,545,536

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Other Comprehensive Income (Loss), Net of Tax	$22,403
Parent Company
Net income / (loss)	20,781	20,767
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	-1,216	238
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	-1,363	-590
Amortization of Other Deferred Charges	1,663	1,691
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	-12,334	-9,322
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax	35,653	24,634
Other Comprehensive Income (Loss), Net of Tax	22,403	16,651
Comprehensive Income / loss, Net of Tax, Including Portion Attributable to Noncontrolling Interest	43,184	37,418
Comprehensive (income) / loss, Net of Tax, Attributable to Noncontrolling Interest	-8,821	-5,635
Comprehensive income / (loss), Net of Tax, Attributable to Parent	34,363	31,783
BIOMED REALTY, L.P.
Net income / (loss)	20,781	20,767
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	-1,216	238
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	-1,363	-590
Amortization of Other Deferred Charges	1,663	1,691
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	-12,334	-9,322
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax	35,653	24,634
Other Comprehensive Income (Loss), Net of Tax	22,403	16,651
Comprehensive Income / loss, Net of Tax, Including Portion Attributable to Noncontrolling Interest	43,184	37,418
Comprehensive (income) / loss, Net of Tax, Attributable to Noncontrolling Interest	-7,655	-4,757
Comprehensive income / (loss), Net of Tax, Attributable to Parent	35,529	32,661
Interest Rate Swaps | Parent Company
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	-1,363
Interest Rate Swaps | BIOMED REALTY, L.P.
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	($1,363)

Consolidated_Statement_of_Equi

Consolidated Statement of Equity (USD $)	Parent Company	BIOMED REALTY, L.P.	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss)/Income	Accumulated Other Comprehensive (Loss)/Income	Dividends in Excess of Earnings	Total Stockholders'/Partner's Equity	Total Stockholders'/Partner's Equity	Noncontrolling Interest	Noncontrolling Interest	Limited Partner	General Partner [Member]	Forward Starting Swaps	Forward Starting Swaps	Interest Rate Swaps	Interest Rate Swaps
In Thousands, except Share data, unless otherwise specified			Parent Company	Parent Company	Parent Company	BIOMED REALTY, L.P.	Parent Company	Parent Company	BIOMED REALTY, L.P.	Parent Company	BIOMED REALTY, L.P.	Common Stock	Common Stock	Parent Company	BIOMED REALTY, L.P.	Parent Company	BIOMED REALTY, L.P.
												BIOMED REALTY, L.P.	BIOMED REALTY, L.P.
Balance - value - period start at Dec. 31, 2014	$3,069,942	$3,069,942	$1,975	$3,649,235	($2,214)	$878	($645,983)	$3,003,013	$3,048,613	$66,929	$21,329	$45,600	$3,002,135
Balance - units - period start at Dec. 31, 2014												5,405,474	197,442,432
Balance - shares - period start at Dec. 31, 2014			197,442,432
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of unvested restricted common stock/OP units - shares			356,596										356,596
Net issuances of unvested restricted common stock/OP units - value	-5,321	-5,321	4	-5,325				-5,321	-5,321				-5,321
Stockholders' Equity, Other				-793				-793		793
Partners' Capital, Other												1,502	-1,502
Stock Issued During Period, Shares, Conversion of Convertible Securities	5,764,026		5,764,026										5,764,026
Stock Issued During Period, Value, Conversion of Convertible Securities, Net of Adjustments	95,756	95,756	57	95,699				95,756	95,756				95,756
Vesting of share-based awards	8,007	8,007		8,007				8,007	8,007				8,007
Common stock dividends	-52,926						-52,926	-52,926
Distribution Made to Limited Partner, Cash Distributions Declared	1,405									1,405		1,405
General Partner Distributions													52,926
Partners' Capital Account, Return of Capital		54,331							54,331
OP unit distributions	-159	-159								-159	-159
Marketable Securities, Realized Gain (Loss)	-12,334	-12,334			-9,895	-9,895		-9,895	-9,895	-2,439	-2,439
Net income / (loss)	20,781	20,781					17,345	17,345	17,802	3,436	2,979	457	17,345
Other Comprehensive Income (Loss), Foreign currency translation adjustment	-1,216	-1,216			-1,185	-1,216		-1,185	-1,216	-31
Unrealized loss on equity securities	35,653	35,653			27,806	28,538		27,806	28,538	7,847	7,115
Amortization of deferred interest costs					1,620	1,663		1,620	1,663	43				1,663	1,663
Unrealized gain on derivative instruments, net	-1,363	-1,363			-1,328	-1,363		-1,328	-1,363	-35						-1,363	-1,363
Balance - value - period end at Mar. 31, 2015	$3,157,078	$3,157,078	$2,036	$3,746,823	$14,804	$18,605	($681,564)	$3,082,099	$3,128,253	$74,979	$28,825	$46,154	$3,063,494
Balance - units - period end at Mar. 31, 2015												5,405,474	203,563,054
Balance - shares - period end at Mar. 31, 2015			203,563,054

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Parent Company
Interest Paid, Capitalized	$6,781	$4,192
Operating Activities
Net income / (loss)	20,781	20,767
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	67,080	62,409
Allowance for doubtful accounts	297	526
Marketable Securities, Realized Gain (Loss), Excluding Other than Temporary Impairments	-12,334	-9,322
Non-cash revenue adjustments	448	481
Other non-cash adjustments	3,147	4,436
Compensation expense related to restricted common stock and LTIP units / share-based payments	8,007	3,750
Distributions representing a return on capital from unconsolidated partnerships	285	203
Change in operating assets and liabilities
Accounts receivable	1,128	-2,482
Accrued straight-line rents	-657	-4,676
Deferred leasing costs	-5,665	-1,754
Other assets	2,288	1,206
Accounts payable, accrued expenses and other liabilities	-8,142	2,194
Net cash provided by operating activities	76,663	77,738
Investing activities
Purchases of investments in real estate and related intangible assets	-89,700
Capital expenditures	-70,753	-69,843
Contributions from historic tax credit transactions, net of deferred costs		15,502
Draws on construction loan receivable	-1,278	-39,584
Contributions to unconsolidated partnerships, net	-57	-4
Purchases of debt and equity securities	-6,151	-2,971
Proceeds from the sale of debt and equity securities	13,696	13,952
Payments for (Proceeds from) Deposits on Real Estate Acquisitions		-16,100
Net cash used in investing activities	-154,243	-99,048
Financing activities
Payments of deferred loan costs	-61
Unsecured line of credit proceeds	162,000	130,000
Unsecured line of credit payments	-20,000	-32,000
Mortgage notes proceeds	9,525
Principal payments on mortgage notes payable	-2,514	-2,776
Distributions to operating partnership unit and LTIP unit holders	-1,564	-1,354
Dividends paid to common stockholders / unitholders	-51,335	-48,029
Net cash provided by financing activities	96,051	45,841
Effect of exchange rate changes on cash and cash equivalents	-172	-116
Net increase / (decrease) in cash and cash equivalents	18,299	24,415
Cash and cash equivalents at beginning of period	46,659	34,706
Cash and cash equivalents at end of period	64,958	59,121
Supplemental disclosure of cash flow information:
Cash paid during the period for interest (net of amounts capitalized of $6,781 and $4,192, for the three months ended March 31, 2015 and 2014, respectively)	11,288	21,593
Supplemental disclosure of non-cash investing and financing activities:
Accrual for common stock dividends / unit distributions declared	52,926	48,128
Accrual for distributions declared for operating partnership unit and LTIP unit holders	1,405	1,351
Accrued additions to real estate and related intangible assets	69,496	60,171
Stock Issued During Period, Value, Conversion of Convertible Securities	95,678
Deposits applied for acquisitions	3,537
BIOMED REALTY, L.P.
Interest Paid, Capitalized	6,781	4,192
Operating Activities
Net income / (loss)	20,781	20,767
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	67,080	62,409
Allowance for doubtful accounts	297	526
Gain (Loss) on Sale of Properties	0
Marketable Securities, Realized Gain (Loss), Excluding Other than Temporary Impairments	-12,334	-9,322
Non-cash revenue adjustments	448	481
Other non-cash adjustments	3,147	4,436
Compensation expense related to restricted common stock and LTIP units / share-based payments	8,007	3,750
Distributions representing a return on capital from unconsolidated partnerships	285	203
Change in operating assets and liabilities
Accounts receivable	1,128	-2,482
Accrued straight-line rents	-657	-4,676
Deferred leasing costs	-5,665	-1,754
Other assets	2,288	1,206
Accounts payable, accrued expenses and other liabilities	-8,142	2,194
Net cash provided by operating activities	76,663	77,738
Investing activities
Purchases of investments in real estate and related intangible assets	-89,700
Capital expenditures	-70,753	-69,843
Contributions from historic tax credit transactions, net of deferred costs		15,502
Draws on construction loan receivable	-1,278	-39,584
Contributions to unconsolidated partnerships, net	-57	-4
Purchases of debt and equity securities	-6,151	-2,971
Proceeds from the sale of debt and equity securities	13,696	13,952
Payments for (Proceeds from) Deposits on Real Estate Acquisitions		-16,100
Net cash used in investing activities	-154,243	-99,048
Financing activities
Payments of deferred loan costs	-61
Unsecured line of credit proceeds	162,000	130,000
Unsecured line of credit payments	-20,000	-32,000
Mortgage notes proceeds	9,525
Principal payments on mortgage notes payable	-2,514	-2,776
Dividends paid to common stockholders / unitholders	-52,899	-49,383
Net cash provided by financing activities	96,051	45,841
Effect of exchange rate changes on cash and cash equivalents	-172	-116
Net increase / (decrease) in cash and cash equivalents	18,299	24,415
Cash and cash equivalents at beginning of period	46,659	34,706
Cash and cash equivalents at end of period	64,958	59,121
Supplemental disclosure of cash flow information:
Cash paid during the period for interest (net of amounts capitalized of $6,781 and $4,192, for the three months ended March 31, 2015 and 2014, respectively)	11,288	21,593
Supplemental disclosure of non-cash investing and financing activities:
Accrual for common stock dividends / unit distributions declared	54,331	49,479
Accrued additions to real estate and related intangible assets	69,496	60,171
Stock Issued During Period, Value, Conversion of Convertible Securities	95,678
Deposits applied for acquisitions	$3,537

Organization_of_the_Parent_Com

Organization of the Parent Company and Description of Business	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization of the Parent Company and Description of Business	Organization of the Parent Company and Description of Business
	BioMed Realty Trust, Inc., a Maryland corporation (the “Parent Company”), operates as a fully integrated, self-administered and self-managed real estate investment trust (“REIT”) focused on acquiring, developing, owning, leasing and managing laboratory and office space for the life science industry principally through its subsidiary, BioMed Realty, L.P., a Maryland limited partnership (the “Operating Partnership” and together with the Parent Company referred to as the “Company”). The Company’s tenants primarily include biotechnology and pharmaceutical companies, scientific research institutions, government agencies and other entities involved in the life science industry. The Company’s properties are generally located in markets with well-established reputations as centers for scientific research, including Boston, San Francisco, San Diego, Maryland, New York/New Jersey, Pennsylvania, North Carolina, Seattle, Cambridge (United Kingdom) and research parks located near or adjacent to universities and their related medical systems.
	The Parent Company is the sole general partner of the Operating Partnership and, as of March 31, 2015, owned a 97.5% interest in the Operating Partnership. The remaining 2.5% interest in the Operating Partnership is held by limited partners. Each partner’s percentage interest in the Operating Partnership is determined based on the number of operating partnership units and long-term incentive plan units (“LTIP units” and together with the operating partnership units, the “OP units”) owned as compared to total OP units (and potentially issuable OP units, as applicable) outstanding as of each period end and is used as the basis for the allocation of net income or loss to each partner.

Basis_of_Presentation_and_Summ

Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies
	The accompanying interim financial statements are unaudited, but have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") for interim financial information and in conjunction with the rules and regulations of the U.S. Securities and Exchange Commission. Accordingly, they do not include all the disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments and eliminations, consisting of normal recurring adjustments necessary for a fair presentation of the financial statements for these interim periods have been recorded. These financial statements should be read in conjunction with the audited consolidated financial statements and notes therein included in the Company's annual report on Form 10-K for the year ended December 31, 2014.
	Reclassifications
	Certain reclassifications have been made to prior period amounts to conform to current period presentation. Such reclassifications have no effect on net income as previously reported.
	Principles of Consolidation
	The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, partnerships and limited liability companies it controls, and variable interest entities (“VIEs”) for which the Company has determined itself to be the primary beneficiary. All material intercompany transactions and balances have been eliminated. The Company consolidates entities the Company controls and records a noncontrolling interest for the portions not owned by the Company. Control is determined, where applicable, by the sufficiency of equity invested and the rights of the equity holders, and by the ownership of a majority of the voting interests, with consideration given to the existence of approval or veto rights granted to the minority stockholder. If the minority stockholder holds substantive participating rights, it overcomes the presumption of control by the majority voting interest holder. In contrast, if the minority stockholder simply holds protective rights (such as consent rights over certain actions), it does not overcome the presumption of control by the majority voting interest holder.
	Assets and liabilities of subsidiaries outside the United States with non-U.S. dollar functional currencies are translated into U.S. dollars using exchange rates as of the balance sheet dates. Income and expenses are translated using the average exchange rates for the reporting period. Foreign currency translation adjustments are recorded as a component of other comprehensive income. For the three months ended March 31, 2015 and 2014, total revenues from properties outside the United States were $4.2 million and $4.8 million, respectively, which represented 2.4% and 2.8% of the Company's total revenues during the respective periods. The Company’s net investments in properties outside the United States were $203.7 million and $200.2 million at March 31, 2015 and December 31, 2014, respectively.
	Investments in Partnerships and Limited Liability Companies
	The Company has determined that it is the primary beneficiary in six VIEs (excluding certain VIEs associated with tax credits discussed below), consisting of single-tenant properties in which the tenant has a purchase option, which are consolidated and reflected in the accompanying consolidated financial statements. Selected financial data of the VIEs at March 31, 2015 and December 31, 2014 consist of the following (in thousands):
		March 31,				December 31,
		2015				2014
	Investment in real estate, net	$	430,343			$	433,842
	Total assets	491,610				493,066
	Total debt	188,780				189,848
	Total liabilities	202,592				203,529
	Historic Tax Credits and New Market Tax Credits
	The Company is a party to certain contractual arrangements with tax credit investors ("TCIs") that were established to enable the TCIs to receive benefits of historic tax credits ("HTCs") and/or new market tax credits ("NMTCs") for certain properties owned by the Company. At March 31, 2015 and December 31, 2014, the Company owned ten properties that had syndicated HTCs or NMTCs, or both, to TCIs.
	Capital contributions are made by TCIs into special purpose entities that ultimately invest these funds in the entity that owns the subject property that generates the tax credits. The TCIs are allocated substantially all of the tax credits and hold only a noncontrolling interest in the economic risk and rewards of the special purpose entities. HTCs are delivered to the TCI upon substantial completion of the project. NMTCs are allowed for up to 39% of a qualified investment and are delivered to the TCI after the investment has been funded and spent on a qualified business. HTCs are subject to 20% recapture per year beginning one year after the completion of the historic rehabilitation of the subject property. NMTCs are subject to 100% recapture until the end of the seventh year following the qualifying investment. The Company has provided the TCIs with certain guarantees which protect the TCIs from loss should a tax credit recapture event occur. The contractual arrangements with the TCIs include a put/call provision whereby the Company may be obligated or entitled to repurchase the ownership interest of the TCIs in the special purpose entities at the end of the tax credit recapture period. The Company anticipates that either the TCIs will exercise their put rights or the Company will exercise its call rights; however, the Company believes that the put rights are more likely to be exercised.
	The portion of the TCI’s capital contribution that is attributed to the put is recorded at fair-value at inception and is accreted to the expected put price as interest expense in the consolidated statements of income. At each of March 31, 2015 and December 31, 2014, approximately $5.2 million of put liabilities were included in other liabilities in the consolidated balance sheets. The remaining balance of the TCI’s capital contribution is initially recorded in other liabilities in the consolidated balance sheets and is reclassified, upon delivery of the tax credit to the TCI, as a reduction in the carrying value of the subject property, net of allocated expenses. During the three months ended March 31, 2014, $15.5 million of tax credits, net of costs and estimated put payments, were contributed by TCIs and were recorded as other liabilities in the consolidated balance sheets. During the three months ended March 31, 2014, $12.8 million of tax credits had been delivered to the TCIs and were reclassified as a reduction of the carrying value of the subject property. Direct and incremental costs incurred in structuring the transaction, consisting of third-party legal, accounting and other professional fees, are deferred and will be recognized as an increase in the cost basis of the subject property upon the recognition of the related tax credit as discussed above.
	At March 31, 2015 and December 31, 2014, the Company determined that the special purpose entity owning one property under development is a VIE, since there is insufficient capital to finance the remaining development activities without further subordinated financial support. The Company has determined it is the primary beneficiary of this VIE, because it has the authority to direct the activities which most significantly impact its economic performance. Selected financial data of the VIE at March 31, 2015 and December 31, 2014 consisted of the following (in thousands):
		March 31,			December 31,
		2015			2014
	Investment in real estate, net	$	5,764		$	2,507
	Total assets	22,720			24,478
	Total liabilities	6,679			7,467
	Investments in Real Estate, Net
	Investments in real estate, net consisted of the following (in thousands):
		March 31,				December 31,
		2015				2014
	Land	$	643,041			$	704,958
	Land under development	225,846				151,242
	Buildings and improvements	4,909,684				4,877,135
	Construction in progress	738,603				629,679
		6,517,174				6,363,014
	Accumulated depreciation	(999,545		)		(946,439		)
		$	5,517,629			$	5,416,575
	Impairment of Long-Lived Assets and Long-Lived Assets to be Disposed
	The Company reviews long-lived assets and certain identifiable intangibles for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The review of recoverability is based on an estimate of the future undiscounted cash flows (excluding interest charges) expected to result from the long-lived asset’s use and eventual disposition. These cash flows consider factors such as expected future operating income, trends and prospects, as well as the effects of leasing demand, competition and other factors. If impairment exists due to the inability to recover the carrying value of a long-lived asset, an impairment loss is recorded to the extent that the carrying value exceeds the estimated fair-value of the property. The Company is required to make subjective assessments as to whether there are impairments in the values of its investments in long-lived assets. These assessments have a direct impact on the Company’s net income because recording an impairment loss results in an immediate negative adjustment to net income. The evaluation of anticipated cash flows is highly subjective and is based in part on assumptions regarding future occupancy, rental rates and capital requirements that could differ materially from actual results in future periods. Although the Company’s strategy is to hold its properties over the long-term, if the Company’s strategy changes or market conditions otherwise dictate an earlier sale date, an impairment loss may be recognized to reduce the property to the lower of the carrying amount or fair-value, and such loss could be material. As of and for the three months ended March 31, 2015, no assets have been identified as impaired and no such impairment losses have been recognized.
	Deferred Leasing Costs, Net
	Leasing commissions and other direct costs associated with obtaining new or renewal leases are recorded at cost and amortized on a straight-line basis over the terms of the respective leases, with remaining terms ranging from less than one year to approximately 20 years as of March 31, 2015. Deferred leasing costs also include the net carrying value of acquired in-place leases and acquired management agreements.
	Deferred leasing costs, net at March 31, 2015 consisted of the following (in thousands):
		Balance at				Accumulated
		March 31, 2015				Amortization			Net
	Acquired in-place leases	$	420,032			$	(280,148	)	$	139,884
	Acquired management agreements	25,801				(23,097		)	2,704
	Deferred leasing and other direct costs	119,250				(42,289		)	76,961
		$	565,083			$	(345,534	)	$	219,549
	Deferred leasing costs, net at December 31, 2014 consisted of the following (in thousands):
		Balance at				Accumulated
		December 31, 2014				Amortization			Net
	Acquired in-place leases	$	415,389			$	(271,782	)	$	143,607
	Acquired management agreements	25,801				(22,328		)	3,473
	Deferred leasing and other direct costs	111,290				(38,657		)	72,633
		$	552,480			$	(332,767	)	$	219,713
	Investments
	Investments in equity securities, which are included in other assets on the accompanying consolidated balance sheets, consisted of the following (in thousands):
		March 31,				December 31,
		2015				2014
	Available-for-sale securities, historical cost	$	14,309			$	10,280
	Unrealized gain, net	71,662				48,341
	Available-for-sale securities, fair-value (1)	85,971				58,621
	Privately-held securities, cost basis	43,895				43,428
	Total equity securities	$	129,866			$	102,049
	-1	Determination of fair-value is classified as Level 1 in the fair-value hierarchy based on the use of quoted prices in active markets.
The Company holds investments in available-for-sale securities of certain publicly-traded companies. Changes in the fair-value of investments classified as available-for-sale are recorded in comprehensive income. The fair-value of the Company's equity investments in publicly-traded companies are based upon the closing trading price of the equity security as of the balance sheet date. Certain of these investments have fair-values less than the Company’s cost basis, net of previous other-than-temporary impairment in these securities due to decreases in their respective stock prices during the three months ended March 31, 2015. However, management has the intent and ability to retain the investments for a period of time sufficient to allow for an anticipated recovery in their market value. Management will continue to periodically evaluate whether any investment, the fair-value of which is less than the Company’s cost basis, should be considered other-than-temporarily impaired. If other-than-temporary impairment is considered to exist, the related unrealized loss will be reclassified from accumulated other comprehensive loss and recorded as a reduction of net income.
The Company also holds investments in securities of certain privately-held companies and funds, which are recorded at cost basis due to the Company’s lack of control or significant influence over such companies and funds.
During the three months ended March 31, 2015, the Company recorded impairment charges of $292,000. Impairment charges are included in other expense in the consolidated statements of income and relate to the Company’s investment in a publicly-traded company. Other than this investment, there were no identified events or changes in circumstances that may have a significant adverse effect on the carrying value of the Company’s cost basis investments and therefore, no evaluation of impairment was performed during the three months ended March 31, 2015 on the Company’s remaining cost basis investments.
In April 2015, the Company received $57.1 million of proceeds from the sale of an investment in a publicly-traded company, resulting in a realized gain on sale of $43.8 million, net of allocation to a noncontrolling interest.
Construction Loan Receivable
The Company had a $255.0 million interest in a $355.0 million construction loan secured by first priority mortgages on a 1.1 million square foot laboratory, office and retail development project located in Boston, Massachusetts, which is 95% leased to Vertex Pharmaceuticals Incorporated to serve as its new corporate headquarters (the "Construction Loan"). In May 2014, the borrower repaid the then outstanding principal and accrued interest balance prior to maturity, of which the Company's portion was approximately $191.2 million.
Lease Termination
During the three months ended March 31, 2015 and 2014, the Company recorded lease termination revenue, net of write-offs of lease intangibles, included in other revenue on the consolidated statements of income of approximately $16.2 million and $5.5 million, respectively. Lease termination revenue for the three months ended March 31, 2015 primarily related to the early termination of Vertex Pharmaceuticals' leases at three of the Company's properties in Cambridge, Massachusetts. Lease termination revenue for the three months ended March 31, 2014 primarily related to the early termination of leases at the Company's 4570 Executive Drive property.
Management’s Estimates
Management has made a number of estimates and assumptions relating to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reporting of revenue and expenses during the reporting period to prepare these consolidated financial statements in conformity with GAAP. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and reported amounts of revenue and expenses that are not readily apparent from other sources. Actual results could differ from those estimates under different assumptions or conditions.
Recent Accounting Pronouncements
In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) 2014-09, Revenue From Contracts With Customers (“ASU 2014-09”), which outlines a comprehensive model for entities to use in accounting for revenue arising from contracts with customers. ASU 2014-09 states that “an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.” While ASU 2014-09 specifically references contracts with customers, it may apply to certain other transactions such as the sale of real estate or equipment. ASU 2014-09 is effective for the Company beginning January 1, 2017, although on April 1, 2015, the FASB proposed a one-year deferral of the effective date. The Company does not expect the adoption of this standard to have a significant impact on the consolidated financial statements as a substantial portion of the Company's revenue consists of rental income from leasing arrangements, which are specifically excluded from ASU 2014-09.
In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis (“ASU 2015-02”), which makes certain changes to both the variable interest model and the voting model, including changes to (1) the identification of variable interests (fees paid to a decision maker or service provider), (2) the variable interest entity characteristics for a limited partnership or similar entity and (3) the primary beneficiary determination. ASU 2015-02 is effective for the Company beginning January 1, 2016. Early adoption is permitted. The Company does not expect the adoption of this standard to have a significant impact on the consolidated financial statements.
In April 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs ("ASU 2015-03"), which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected. ASU 2015-03 is effective for the Company beginning January 1, 2016. Early adoption is permitted. Upon adoption, the Company will apply the new standard on a retrospective basis and adjust the balance sheet of each individual period to reflect the period-specific effects of applying the new standard. The Company does not expect the adoption of this standard to have a significant impact on the consolidated financial statements.

Equity_of_the_Parent_Company

Equity of the Parent Company	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Equity of the Parent Company	Equity of the Parent Company
	During the three months ended March 31, 2015, the Parent Company issued restricted stock awards to the Company’s employees totaling 586,674 shares of common stock (237,789 shares of common stock were surrendered to the Company and subsequently retired in lieu of cash payments for taxes due on the vesting of restricted stock), which are included in the total of common stock outstanding as of the period end.
	The Parent Company awarded units to certain of its executive officers (the “Performance Units”), which represent a contingent right to receive one share of the Parent Company’s common stock if vesting conditions are satisfied. Outstanding Performance Units vest ratably over two or three year periods (each, a “Performance Period”) based upon the Parent Company’s total stockholder return relative to its peer group (the "Market Conditions"). The grant date fair-value of the Performance Units was estimated using a Monte Carlo simulation which considered the likelihood of achieving the Market Conditions. The expected value of the Performance Units on the grant date was determined by simulating the total stockholder return for the Parent Company and the peer group, considering the stock price variance for each of the peer group companies compared to each other and the Parent Company. In January 2015, 136,296 Performance Units which were originally granted to certain executive officers in January 2012 and represent the maximum number of Performance Units that could have vested, were forfeited as a result of the Parent Company's total stockholder return relative to its peer group for the three years ending December 31, 2014 being below the threshold for any payout. In addition, of the 203,144 Performance Units which were originally granted to certain executive officers in January 2013 and represent the maximum number of Performance Units that could have vested, 13,215 Performance Units vested (resulting in the issuance of 13,215 shares of the Parent Company’s common stock, of which 5,504 shares were surrendered to the Company and subsequently retired in lieu of cash payments for taxes due on such vesting) and the remaining 189,929 Performance Units were forfeited, based on the Parent Company’s total stockholder return relative to its peer group for the two years ending December 31, 2014. During the three months ended March 31, 2015, the Parent Company awarded 370,880 Performance Units which represent the maximum number of Performance Units that may vest over a three-year Performance Period ending December 31, 2017. The grant date fair-value of these awards of approximately $5.4 million will be recognized as compensation expense on a straight-line basis over the three-year Performance Period. The total unearned compensation remaining on the Performance Units granted during the three months ended March 31, 2015 to be expensed in future periods over a weighted-average term of 2.8 years was $3.8 million as of March 31, 2015. No dividends will be paid or accrued on the Performance Units, and shares of the Parent Company's common stock will not be issued until vesting of the Performance Units occurs.
	Common Stock, Operating Partnership Units and LTIP Units
	As of March 31, 2015, the Company had outstanding 203,563,054 shares of the Parent Company’s common stock and 5,083,400 and 322,074 operating partnership and LTIP units, respectively (excluding operating partnership units held by the Parent Company). A share of the Parent Company’s common stock and the operating partnership and LTIP units have essentially the same economic characteristics as they share equally in the total net income or loss and distributions of the Operating Partnership.
	Dividends and Distributions
	The following table lists the dividends and distributions declared by the Parent Company and the Operating Partnership during the three months ended March 31, 2015:
	Declaration Date		Securities Class		Amount Per				Period Covered		Dividend and		Dividend and
					Share/Unit						Distribution		Distribution Amount
											Payable Date
													(In thousands)
	March 16, 2015		Common stock and OP units		$	0.26			January 1, 2015 to March 31, 2015		April 15, 2015		$	54,331
	Changes in Accumulated Other Comprehensive Income / (Loss) by Component
	The following table shows the changes in accumulated other comprehensive income / (loss) for the Parent Company for the three months ended March 31, 2015, by component (in thousands):
		Foreign currency translation adjustments				Unrealized gains on available-for-sale securities				Gain / (loss) on derivative instruments				Total
	Balance at December 31, 2014	$	2,309			$	37,705			$	(42,228	)		$	(2,214	)
	Other comprehensive (loss) / income before reclassifications	(1,216		)		35,653				(2,202		)		32,235
	Amounts reclassified from accumulated other comprehensive income (1)	—				(12,334		)		2,502				(9,832		)
	Net other comprehensive (loss) / income	(1,216		)		23,319				300				22,403
	Net other comprehensive loss / (income) allocable to noncontrolling interests	31				(5,408		)		(8		)		(5,385		)
	Balance as of March 31, 2015	$	1,124			$	55,616			$	(41,936	)		$	14,804
	-1	Amounts reclassified from unrealized gain on available-for-sale securities are included in other income, net in the consolidated statements of income. Amounts reclassified from loss on derivative instruments are included in interest expense, net in the consolidated statements of income. See Note 9 for further information.
	Noncontrolling Interests
	Noncontrolling interests on the consolidated balance sheets of the Parent Company relate primarily to the OP units in the Operating Partnership that are not owned by the Parent Company. With respect to the noncontrolling interests in the Operating Partnership, noncontrolling interests with redemption provisions that permit the issuer to settle in either cash or common stock at the option of the issuer are further evaluated to determine whether temporary or permanent equity classification on the balance sheet is appropriate. Because the OP units comprising the noncontrolling interests contain such a provision, the Company evaluated this guidance, including the requirement to settle in unregistered shares, and determined that the OP units meet the requirements to qualify for presentation as permanent equity.
	The Company evaluates individual redeemable noncontrolling interests for the ability to continue to recognize the noncontrolling interest as permanent equity in the consolidated balance sheets. Any redeemable noncontrolling interest that fails to qualify as permanent equity will be reclassified as temporary equity and adjusted to the greater of (1) the carrying amount, or (2) its redemption value at the end of the period in which the determination is made.
	The redemption value of the OP units not owned by the Parent Company, had such units been redeemed at March 31, 2015, was approximately $122.7 million based on the average closing price of the Parent Company’s common stock of $22.69 per share for the ten consecutive trading days immediately preceding March 31, 2015.
	The following table shows the vested ownership interests in the Operating Partnership:
		March 31, 2015						December 31, 2014
		Operating Partnership Units and LTIP Units			Percentage of Total			Operating Partnership Units and LTIP Units			Percentage of Total
	BioMed Realty Trust	202,174,206			97.5	%		196,031,538			97.4	%
	Noncontrolling interest consisting of:
	Operating partnership and LTIP units held by employees and related parties	2,645,888			1.3	%		2,645,888			1.3	%
	Operating partnership and LTIP units held by third parties	2,627,145			1.2	%		2,627,145			1.3	%
	Total	207,447,239			100	%		201,304,571			100	%

Capital_of_the_Operating_Partn

Capital of the Operating Partnership	3 Months Ended
	Mar. 31, 2015
Partners' Capital [Abstract]
Capital of the Operating Partnership	Capital of the Operating Partnership
	Operating Partnership Units and LTIP Units
	As of March 31, 2015, the Operating Partnership had outstanding 208,646,454 operating partnership units and 322,074 LTIP units. The Parent Company owned 97.5% of the partnership interests in the Operating Partnership at March 31, 2015, is the Operating Partnership’s general partner and is responsible for the management of the Operating Partnership’s business. As the general partner of the Operating Partnership, the Parent Company effectively controls the ability to issue common stock of the Parent Company upon a limited partner’s notice of redemption. In addition, the Parent Company has generally acquired OP units upon a limited partner’s notice of redemption in exchange for shares of its common stock. The redemption provisions of OP units owned by limited partners that permit the Parent Company to settle in either cash or common stock at the option of the Parent Company are further evaluated in accordance with applicable accounting guidance to determine whether temporary or permanent equity classification on the balance sheet is appropriate. The Operating Partnership evaluated this guidance, including the requirement to settle in unregistered shares, and determined that these OP units meet the requirements to qualify for presentation as permanent equity.
	The redemption value of the OP units owned by the limited partners, not including the Parent Company, had such units been redeemed at March 31, 2015, was approximately $122.7 million based on the average closing price of the Parent Company’s common stock of $22.69 per share for the ten consecutive trading days immediately preceding March 31, 2015.
	Changes in Accumulated Other Comprehensive Income / (Loss) by Component
	The following table shows the changes in accumulated other comprehensive income / (loss) for the Operating Partnership for the three months ended March 31, 2015, by component (in thousands):
		Foreign currency translation adjustments			Unrealized gains on available- for-sale securities			Gain / (loss) on derivative instruments			Total
	Balance at December 31, 2014	$	2,367		$	38,732		$	(40,221	)	$	878
	Other comprehensive (loss) / income before reclassifications	(1,216		)	35,653			(2,202		)	32,235
	Amounts reclassified from accumulated other comprehensive income (1)	—			(12,334		)	2,502			(9,832		)
	Net other comprehensive (loss) / income	(1,216		)	23,319			300			22,403
	Net other comprehensive income allocable to noncontrolling interest	—			(4,676		)	—			(4,676		)
	Balance as of March 31, 2015	$	1,151		$	57,375		$	(39,921	)	$	18,605
	-1	Amounts reclassified from unrealized gain on available-for-sale securities are included in other income, net in the the consolidated statements of income. Amounts reclassified from loss on derivative instruments are included in interest expense, net in the consolidated statements of income. See Note 9 for further information.

Debt

Debt	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Debt	Debt
	Debt of the Parent Company
	The Parent Company does not hold any indebtedness. All debt is held directly or indirectly by the Operating Partnership; however, the Parent Company has guaranteed the Operating Partnership’s Unsecured Senior Notes due 2016 (the “Notes due 2016”), Unsecured Senior Notes due 2019 (the "Notes due 2019"), Unsecured Senior Notes due 2020 (the “Notes due 2020”), Unsecured Senior Notes due 2022 (the “Notes due 2022”), Unsecured Senior Term Loan due 2017 (the “Term Loan due 2017”), Unsecured Senior Term Loan due 2018 (the “Term Loan due 2018”) and unsecured line of credit.
	Debt of the Operating Partnership
	The following is a summary of the Operating Partnership’s outstanding consolidated debt as of March 31, 2015 and December 31, 2014 (dollars in thousands):
		Stated Interest Rate		Effective Interest Rate		Principal Balance
						March 31,			December 31,			Maturity Date
						2015			2014
	Mortgage Notes Payable
	9900 Belward Campus Drive	5.64	%	3.99	%	$	10,447		$	10,486		July 1, 2017
	9901 Belward Campus Drive	5.64	%	3.99	%	12,864			12,913			July 1, 2017
	100 College Street	2.4	%	2.4	%	91,882			82,210			August 2, 2016
	4320 Forest Park Avenue	4	%	2.7	%	21,000			21,000			June 30, 2015
	300 George Street	6.2	%	4.91	%	44,615			45,052			July 1, 2025
	Hershey Center for Applied Research	6.15	%	4.71	%	12,803			12,938			May 5, 2027
	500 Kendall Street (Kendall D)	6.38	%	5.45	%	54,548			55,545			December 1, 2018
	Shady Grove Road	5.97	%	5.97	%	140,599			141,131			September 1, 2016
	University of Maryland BioPark I	5.93	%	4.69	%	15,871			16,056			May 15, 2025
	University of Maryland BioPark II	5.2	%	4.33	%	61,636			61,905			September 5, 2021
	University of Maryland BioPark Garage	5.2	%	4.33	%	4,639			4,660			September 1, 2021
	University of Miami Life Science & Technology Park	4	%	2.89	%	20,000			20,000			February 1, 2016
						490,904			483,896
	Unamortized premiums					12,296			12,861
	Mortgage notes payable, net					503,200			496,757
	Exchangeable Senior Notes (1)	3.75	%	3.75	%	—			95,678			January 30, 2015
	Notes due 2016	3.85	%	3.99	%	400,000			400,000			April 15, 2016
	Notes due 2019	2.63	%	2.72	%	400,000			400,000			May 1, 2019
	Notes due 2020	6.13	%	6.27	%	250,000			250,000			April 15, 2020
	Notes due 2022	4.25	%	4.36	%	250,000			250,000			July 15, 2022
						1,300,000			1,300,000
	Unamortized discounts					(5,745		)	(6,097		)
	Unsecured senior notes, net					1,294,255			1,293,903
	Term Loan due 2017 - U.S. dollar (2)	1.57	%	2.39	%	243,596			243,596			March 30, 2017
	Term Loan due 2017 - GBP (2)	1.9	%	2.14	%	148,030			155,730			March 30, 2017
	Term Loan due 2018	1.36	%	1.67	%	350,000			350,000			March 24, 2018
	Unsecured senior term loans					741,626			749,326
	Unsecured line of credit (3)	1.27	%	1.27	%	226,000			84,000			March 24, 2018
	Total consolidated debt					$	2,765,081		$	2,719,664
	-1	In January 2015, the entire principal amount of the Operating Partnership's Exchangeable Senior Notes due 2030 (the "Exchangeable Senior Notes") was exchanged for 5,764,026 shares of the Parent Company's common stock, at the request of the holders.
	-2	In August 2012, the Operating Partnership converted approximately $156.4 million of outstanding borrowings into British pounds sterling (“GBP”) equal to £100.0 million, which was designated as a net investment hedge to mitigate the risk of fluctuations in foreign currency exchange rates. The principal balance represents the U.S. dollar amount based on the exchange rates of $1.48 to £1.00 and $1.56 to £1.00 at March 31, 2015 and December 31, 2014, respectively. The effective interest rate includes the impact of interest rate swap agreements (see Note 9 for further discussion of interest rate swap agreements).
	-3	At March 31, 2015, the Operating Partnership had additional borrowing capacity under the unsecured line of credit of up to approximately $674.0 million.
	Exchangeable Senior Notes
	During the three months ended March 31, 2015, at the request of the holders that exercised their exchange right pursuant to the terms of the Exchangeable Senior Notes, the Parent Company issued 5,764,026 shares of its common stock in exchange for the remaining $95.7 million in aggregate principal amount of the Exchangeable Senior Notes.
	Net Investment Hedge
	The Operating Partnership designated the GBP denominated debt under the Term Loan due 2017 as a net investment hedge. The Operating Partnership entered into this net investment hedge to protect a designated amount of the Operating Partnership’s net investment in a GBP functional currency subsidiary against the risk of adverse changes in the GBP/U.S. dollar exchange rate (foreign exchange risk). Variability in the GBP/U.S. dollar exchange rate impacts the Operating Partnership (a U.S. dollar functional currency entity) as the financial statements of the GBP functional currency subsidiary are translated each period, with the effect of changes in the GBP/U.S. dollar exchange rate being recorded in accumulated other comprehensive income. When the net investment is sold or substantially liquidated, the balance of the translation adjustment accumulated in other comprehensive income will be reclassified into earnings. The Operating Partnership is hedging the risk of changes in the U.S. dollar equivalent value of a portion of its net investment in its GBP subsidiary attributable to changes in the GBP/U.S. dollar exchange rate during the period of investment during which the hedging instrument is outstanding.
	Maturities of Long-Term Debt
	As of March 31, 2015, principal payments due for the Operating Partnership’s consolidated indebtedness (excluding debt premiums and discounts) were as follows (in thousands):
	2015	$	28,977
	2016	660,291
	2017	423,932
	2018	623,804
	2019	405,724
	Thereafter	615,802
		$	2,758,530

Earnings_Per_Share_of_the_Pare

Earnings Per Share of the Parent Company	3 Months Ended
	Mar. 31, 2015
Earnings Per Share, Basic and Diluted [Abstract]
Earnings Per Share of the Parent Company	Earnings Per Share of the Parent Company
	Through March 31, 2015 all of the Company’s participating securities (including the OP units) received dividends/distributions at an equal dividend/distribution rate per share/unit. As a result, the portion of net income allocable to the weighted-average unvested restricted stock outstanding for the three months ended March 31, 2015 and 2014 has been deducted from net income attributable to the Company to calculate basic earnings per share attributable to common stockholders. The calculation of diluted earnings per share for the three months ended March 31, 2015 and 2014 includes the outstanding OP units (both vested and unvested) in the weighted-average shares, and net income attributable to noncontrolling interests in the Operating Partnership has been added back to net income attributable to the Company. For the three months ended March 31, 2015 and 2014, the Performance Units were dilutive to the calculation of diluted earnings per share as calculated, assuming that March 31, 2015 and 2014 were the end dates of the respective Performance Units' Performance Periods. For the three months ended March 31, 2015 and 2014, the unvested restricted stock was anti-dilutive to the calculation of diluted earnings per share and was therefore excluded. As a result, diluted earnings per share was calculated based upon net income attributable to the Company less net income allocable to unvested restricted stock and distributions in excess of earnings attributable to unvested restricted stock. In addition, for the three months ended March 31, 2015 and 2014, 1,194,015 and 10,525,410 shares issuable upon settlement of the exchange feature of the Exchangeable Senior Notes, respectively, were anti-dilutive and were not included in the calculation of diluted earnings per share based on the “if converted” method. No other shares were considered anti-dilutive for the three months ended March 31, 2015 or 2014.
	Computations of basic and diluted earnings per share (in thousands, except share data) were as follows:
		Three Months Ended
		March 31,
		2015			2014
	Basic earnings per share:
	Net income attributable to the Company	$	17,345		$	18,833
	Net income allocable and distributions in excess of earnings to participating securities	(393		)	(378		)
	Net income attributable to common stockholders - basic	$	16,952		$	18,455
	Diluted earnings per share:
	Net income attributable to common stockholders - basic	16,952			18,455
	Net income attributable to noncontrolling interests in Operating Partnership	457			521
	Net income attributable to common stockholders - diluted	$	17,409		$	18,976
	Weighted-average common shares outstanding:
	Basic	200,789,795			190,905,867
	Incremental shares from:
	Performance units	340,879			229,295
	Operating partnership and LTIP units	5,405,474			5,410,374
	Diluted	206,536,148			196,545,536
	Basic and diluted earnings per share:
	Net income per share attributable to common stockholders - basic and diluted	$	0.08		$	0.1

Earnings_Per_Unit_of_the_Opera

Earnings Per Unit of the Operating Partnership	3 Months Ended
	Mar. 31, 2015
Partnership Income [Abstract]
Earnings Per Unit of the Operating Partnership	Earnings Per Unit of the Operating Partnership
	Through March 31, 2015, all of the Operating Partnership’s participating securities received distributions at an equal distribution rate per unit. As a result, the portion of net income allocable to the weighted-average unvested OP units outstanding for the three months ended March 31, 2015 and 2014 has been deducted from net income attributable to the Operating Partnership to calculate basic earnings per unit attributable to common unit holders. For the three months ended March 31, 2015 and 2014, the unvested OP units were anti-dilutive to the calculation of earnings per unit and were therefore excluded from the calculation of diluted earnings per unit, and diluted earnings per unit was calculated based upon net income attributable to unit holders. For the three months ended March 31, 2015 and 2014, the Performance Units were dilutive to the calculation of diluted earnings per unit as calculated, assuming that March 31, 2015 and 2014 were the end date of the respective Performance Units’ Performance Periods. In addition, for the three months ended March 31, 2015 and 2014, 1,194,015 and 10,525,410 units issuable upon settlement of the exchange feature of the Exchangeable Senior Notes, respectively, were anti-dilutive and were not included in the calculation of diluted earnings per unit based on the “if converted” method. No other units were considered anti-dilutive for the three months ended March 31, 2015 or 2014.
	Computations of basic and diluted earnings per unit (in thousands, except unit data) were as follows:
		Three Months Ended
		March 31,
		2015			2014
	Basic and diluted earnings per unit:
	Net income attributable to the Operating Partnership	$	17,802		$	19,354
	Net income allocable and distributions in excess of earnings to participating securities	(393		)	(378		)
	Net income attributable to unit holders - basic and diluted	$	17,409		$	18,976
	Weighted-average units outstanding:
	Basic	206,195,269			196,316,241
	Incremental units from:
	Performance units	340,879			229,295
	Diluted	206,536,148			196,545,536
	Basic and diluted earnings per unit:
	Net income per unit attributable to unit holders - basic and diluted	$	0.08		$	0.1

Investment_in_Unconsolidated_P

Investment in Unconsolidated Partnerships	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Partnerships	Investment in Unconsolidated Partnerships
	The accompanying consolidated financial statements include investments in two limited liability companies with Prudential Real Estate Investors (“PREI”), 10165 McKellar Court, L.P. (“McKellar Court”), a limited partnership with Quidel Corporation, the tenant which occupies the McKellar Court property and BioPark Fremont, LLC ("BioPark Fremont"), a limited liability company with RPC Poppleton, LLC. General information on the PREI limited liability companies, the McKellar Court partnership and BioPark Fremont (each referred to in this footnote individually as a “partnership” and collectively as the “partnerships”) as of March 31, 2015 was as follows:
	Name		Partner		Company’s		Company’s		Date Acquired
					Ownership		Economic
					Interest		Interest
	PREI I LLC (1)		PREI		20%		20%		April 4, 2007
	PREI II LLC		PREI		20%		20%		April 4, 2007
	McKellar Court (2)		Quidel Corporation		22%		22%		September 30, 2004
	BioPark Fremont		RPC Poppleton, LLC		50%		50%		May 31, 2013
	-1	PREI I LLC owns two properties in Cambridge, Massachusetts. At March 31, 2015, there were $139.0 million in outstanding borrowings on a secured loan facility held by a wholly-owned subsidiary of PREI I LLC, with a contractual interest rate of 2.23% (including the applicable credit spread) and a maturity date of August 13, 2015 (with an option to extend the maturity date to August 13, 2016 at its discretion after satisfying certain conditions and paying an extension fee).
	-2	The Company’s investment in the McKellar Court partnership (maximum exposure to losses) was approximately $11.8 million at March 31, 2015. The Company’s economic interest in the McKellar Court partnership entitles it to 75% of the extraordinary cash flows after repayment of the partners’ capital contributions and 22% of the operating cash flows.
	The condensed combined balance sheets for all of the Company’s unconsolidated partnerships were as follows (in thousands):
		March 31,				December 31,
		2015				2014
	Assets:
	Investments in real estate, net	$	262,727			$	267,007
	Cash and cash equivalents (including restricted cash)	8,504				6,057
	Other assets	11,445				11,599
	Total assets	$	282,676			$	284,663
	Liabilities and members’ equity:
	Mortgage notes payable and secured loan	$	152,077			$	152,056
	Other liabilities	8,449				9,020
	Members’ equity	122,150				123,587
	Total liabilities and members' equity	$	282,676			$	284,663
	Company’s investments in unconsolidated partnerships	$	34,978			$	35,291
	The selected data and results of operations for the unconsolidated partnerships were as follows (in thousands):
			Three Months Ended
			March 31,
			2015				2014
	Total revenues		$	8,728			$	4,059
	Total expenses		(9,086		)		(6,130		)
	Net loss		$	(358	)		$	(2,071	)
	Company’s equity in net income / (loss) of unconsolidated partnerships		$	153			$	(138	)
	Fees earned by the Company (1)		$	111			$	283
	-1	The Company acts as the operating member or partner, as applicable, and day-to-day manager for the partnerships. The Company is entitled to receive fees for providing construction and development services (as applicable) and management services to the PREI joint ventures, which are reflected in tenant recoveries and other income in the consolidated statements of income.

Derivatives_and_Other_Financia

Derivatives and Other Financial Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Other Financial Instruments	Derivatives and Other Financial Instruments
	The Company is exposed to the effect of changes in interest rates on the Operating Partnership’s U.S. dollar-LIBOR-based and GBP-LIBOR-based debt. The Company limits this risk by following established risk management policies and procedures including the use of derivatives. The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements related to the Operating Partnership’s LIBOR-based debt. To accomplish these objectives, the Company primarily uses interest rate swaps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The interest rate swaps hedge the Company’s exposure to the variability on expected cash flows attributable to changes in interest rates. These interest rate swaps are currently intended to hedge interest payments associated with the Operating Partnership’s Term Loan due 2017 and Term Loan due 2018.
	As of March 31, 2015, the Company had deferred interest costs of approximately $27.0 million in accumulated other comprehensive loss related to forward starting swaps, which were settled with the corresponding counterparties in 2009. The forward starting swaps were entered into to mitigate the Company’s exposure to the variability in expected future cash flows attributable to changes in future interest rates associated with a forecasted issuance of fixed-rate debt, with interest payments for a minimum of ten years. The deferred interest costs will be amortized as additional interest expense over a remaining period of approximately four years.
	The following is a summary of the terms of the interest rate swaps and their respective fair-values (dollars in thousands):
											Fair-Value(1)
		Notional Amount									March 31,			December 31,
						Strike Rate			Effective Date	Expiration Date	2015			2014
	Interest rate swaps	$	200,000			1.163	%		March 30, 2012	March 30, 2017	$	(1,960	)	$	(1,448	)
	Interest rate swaps	200,000				0.701	%		October 1, 2013	October 1, 2016	(569		)	(186		)
	Interest rate swaps(2)	74,015				0.731	%		August 2, 2012	March 30, 2017	59			63
	Interest rate swaps(2)	74,015				0.7425	%		August 2, 2012	March 30, 2017	43			45
	Total interest rate swaps	$	548,030								$	(2,427	)	$	(1,526	)
	-1	Fair-value of derivative instruments does not include any related accrued interest payable, which is included in accrued expenses on the accompanying consolidated balance sheets. Derivative valuations are classified in Level 2 of the fair-value hierarchy. Assets are included in other assets and liabilities are included in accounts payable, accrued expenses and other liabilities on the accompanying consolidated balance sheets.
	-2	Translation to U.S. dollars is based on exchange rates of $1.48 to £1.00 and $1.56 to £1.00 at March 31, 2015 and December 31, 2014, respectively.
	For derivatives designated as cash flow hedges, the effective portion of changes in the fair-value of the derivative is initially reported in other comprehensive income (outside of earnings) and subsequently reclassified to earnings in the period in which the hedged forecasted transaction affects earnings. During the three months ended March 31, 2015 and 2014, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. The ineffective portion of the change in fair-value of the derivatives is recognized directly in earnings. No portion of the derivatives designated as cash flow hedges were classified as ineffective during the three months ended March 31, 2015 or 2014.
	The following is a summary of the amount of gain / (loss) recognized in other comprehensive income related to the derivative instruments (in thousands):
			Three Months Ended
			March 31,
			2015				2014
	Amount of loss recognized in other comprehensive income (effective portion):
	Cash flow hedges
	Interest rate swaps		$	(2,202	)		$	(1,449	)
	Amount of (loss) / income reclassified from accumulated other comprehensive loss to income (effective portion):
	Cash flow hedges
	Interest rate swaps (1)		$	(839	)		$	859
	Forward starting swaps (2)		(1,663		)		1,691
	Total interest rate swaps		$	(2,502	)		$	2,550
	Amount of (loss) / gain recognized in income (ineffective portion and amount excluded from effectiveness testing):
	Other derivative instruments		(170		)		162
	Total (loss) / gain on derivative instruments		$	(170	)		$	162
	-1	Amount represents payments made to swap counterparties for the effective portion of interest rate swaps that were recognized as an increase to interest expense for the periods presented (the amount was recorded as an increase and corresponding decrease to accumulated other comprehensive loss in the same accounting period).
	-2	Amount represents reclassifications of deferred interest costs from accumulated other comprehensive loss to interest expense related to the Company’s previously settled forward starting swaps.

FairValue_of_Financial_Instrum

Fair-Value of Financial Instruments	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair-Value of Financial Instruments	Fair-Value of Financial Instruments
	The Company’s disclosures of estimated fair-value of financial instruments at March 31, 2015 and December 31, 2014 were determined using available market information and appropriate valuation methods. Considerable judgment is necessary to interpret market data and develop estimated fair-value. The use of different market assumptions or estimation methods may have a material effect on the estimated fair-value amounts.
	The carrying amounts for cash and cash equivalents, accounts receivable, accounts payable, accrued expenses and other liabilities approximate fair-value due to the short-term nature of these instruments.
	The Company utilizes quoted market prices to estimate the fair-value of its fixed-rate and variable-rate debt, when available. If quoted market prices are not available, the Company calculates the fair-value of its mortgage notes payable and other fixed-rate debt based on a currently available market rate assuming the loans are outstanding through maturity and considering the collateral. In determining the current market rate for fixed-rate debt, a market credit spread is added to the quoted yields on federal government treasury securities with similar terms to debt. In determining the current market rate for variable-rate debt, a market credit spread is added to the current effective interest rate. The carrying values of interest rate swaps are reflected at their fair-values.
	At March 31, 2015 and December 31, 2014, the aggregate fair-value and the carrying value of the Company’s financial instruments were as follows (in thousands):
		March 31, 2015				December 31, 2014
		Fair-Value (1)		Carrying Value		Fair-Value (1)		Carrying Value
	Mortgage notes payable, net	$	508,782	$	503,200	$	502,115	$	496,757
	Exchangeable Senior Notes	—		—		134,619		95,678
	Notes due 2016, net	409,600		399,435		411,600		399,304
	Notes due 2019, net	402,100		397,984		398,280		397,873
	Notes due 2020, net	285,250		248,512		283,250		248,450
	Notes due 2022, net	260,000		248,324		258,250		248,275
	Term Loan due 2017 - U.S. dollar	244,797		243,596		244,945		243,596
	Term Loan due 2017 - GBP (2)	148,758		148,030		156,589		155,730
	Term Loan due 2018	350,515		350,000		350,557		350,000
	Unsecured line of credit	225,668		226,000		83,866		84,000
	Derivative instruments (3)	2,203		2,203		1,132		1,132
	Available-for-sale securities	85,971		85,971		58,621		58,621
	-1	Fair-values of debt and derivative instruments are classified in Level 2 of the fair-value hierarchy. Fair-value of available-for-sale securities are classified in Level 1 of the fair-value hierarchy.
	-2	The principal balance represents the U.S. dollar amount based on the exchange rate of $1.48 to £1.00 and $1.56 to £1.00 at March 31, 2015 and December 31, 2014, respectively.
	-3	The Company’s derivative instruments are reflected in other assets and in accounts payable, accrued expenses and other liabilities on the accompanying consolidated balance sheets based on their respective balances (see Note 9).

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
Acquisitions	Acquisitions
	The Company acquired one property during the three months ended March 31, 2015. The table below reflects the preliminary purchase price allocation for this acquisition (in thousands).
	Property	Acquisition Date	Investments in Real Estate		Below Market Lease			In-Place Lease		Acquisition Date Fair-Value
	307 Westlake	February 11, 2015	$	85,733	$	(1,824	)	$	5,791	$	89,700
	Weighted average intangible amortization life (in months)				96			95
	Revenues of approximately $1.0 million and net income of $191,183 associated with the 307 Westlake property are included in the consolidated statements of income for the three months ended March 31, 2015 for both the Parent Company and the Operating Partnership.

Basis_of_Presentation_and_Summ1

Basis of Presentation and Summary of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation
	The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, partnerships and limited liability companies it controls, and variable interest entities (“VIEs”) for which the Company has determined itself to be the primary beneficiary. All material intercompany transactions and balances have been eliminated. The Company consolidates entities the Company controls and records a noncontrolling interest for the portions not owned by the Company. Control is determined, where applicable, by the sufficiency of equity invested and the rights of the equity holders, and by the ownership of a majority of the voting interests, with consideration given to the existence of approval or veto rights granted to the minority stockholder. If the minority stockholder holds substantive participating rights, it overcomes the presumption of control by the majority voting interest holder. In contrast, if the minority stockholder simply holds protective rights (such as consent rights over certain actions), it does not overcome the presumption of control by the majority voting interest holder.
	Assets and liabilities of subsidiaries outside the United States with non-U.S. dollar functional currencies are translated into U.S. dollars using exchange rates as of the balance sheet dates. Income and expenses are translated using the average exchange rates for the reporting period. Foreign currency translation adjustments are recorded as a component of other comprehensive income. For the three months ended March 31, 2015 and 2014, total revenues from properties outside the United States were $4.2 million and $4.8 million, respectively, which represented 2.4% and 2.8% of the Company's total revenues during the respective periods. The Company’s net investments in properties outside the United States were $203.7 million and $200.2 million at March 31, 2015 and December 31, 2014, respectively.
Investments in Partnerships and Limited Liability Companies	Investments in Partnerships and Limited Liability Companies
	The Company has determined that it is the primary beneficiary in six VIEs (excluding certain VIEs associated with tax credits discussed below), consisting of single-tenant properties in which the tenant has a purchase option, which are consolidated and reflected in the accompanying consolidated financial statements. Selected financial data of the VIEs at March 31, 2015 and December 31, 2014 consist of the following (in thousands):
		March 31,			December 31,
		2015			2014
	Investment in real estate, net	$	430,343		$	433,842
	Total assets	491,610			493,066
	Total debt	188,780			189,848
	Total liabilities	202,592			203,529
	Historic Tax Credits and New Market Tax Credits
	The Company is a party to certain contractual arrangements with tax credit investors ("TCIs") that were established to enable the TCIs to receive benefits of historic tax credits ("HTCs") and/or new market tax credits ("NMTCs") for certain properties owned by the Company. At March 31, 2015 and December 31, 2014, the Company owned ten properties that had syndicated HTCs or NMTCs, or both, to TCIs.
	Capital contributions are made by TCIs into special purpose entities that ultimately invest these funds in the entity that owns the subject property that generates the tax credits. The TCIs are allocated substantially all of the tax credits and hold only a noncontrolling interest in the economic risk and rewards of the special purpose entities. HTCs are delivered to the TCI upon substantial completion of the project. NMTCs are allowed for up to 39% of a qualified investment and are delivered to the TCI after the investment has been funded and spent on a qualified business. HTCs are subject to 20% recapture per year beginning one year after the completion of the historic rehabilitation of the subject property. NMTCs are subject to 100% recapture until the end of the seventh year following the qualifying investment. The Company has provided the TCIs with certain guarantees which protect the TCIs from loss should a tax credit recapture event occur. The contractual arrangements with the TCIs include a put/call provision whereby the Company may be obligated or entitled to repurchase the ownership interest of the TCIs in the special purpose entities at the end of the tax credit recapture period. The Company anticipates that either the TCIs will exercise their put rights or the Company will exercise its call rights; however, the Company believes that the put rights are more likely to be exercised.
	The portion of the TCI’s capital contribution that is attributed to the put is recorded at fair-value at inception and is accreted to the expected put price as interest expense in the consolidated statements of income. At each of March 31, 2015 and December 31, 2014, approximately $5.2 million of put liabilities were included in other liabilities in the consolidated balance sheets. The remaining balance of the TCI’s capital contribution is initially recorded in other liabilities in the consolidated balance sheets and is reclassified, upon delivery of the tax credit to the TCI, as a reduction in the carrying value of the subject property, net of allocated expenses. During the three months ended March 31, 2014, $15.5 million of tax credits, net of costs and estimated put payments, were contributed by TCIs and were recorded as other liabilities in the consolidated balance sheets. During the three months ended March 31, 2014, $12.8 million of tax credits had been delivered to the TCIs and were reclassified as a reduction of the carrying value of the subject property. Direct and incremental costs incurred in structuring the transaction, consisting of third-party legal, accounting and other professional fees, are deferred and will be recognized as an increase in the cost basis of the subject property upon the recognition of the related tax credit as discussed above.
	At March 31, 2015 and December 31, 2014, the Company determined that the special purpose entity owning one property under development is a VIE, since there is insufficient capital to finance the remaining development activities without further subordinated financial support. The Company has determined it is the primary beneficiary of this VIE, because it has the authority to direct the activities which most significantly impact its economic performance. Selected financial data of the VIE at March 31, 2015 and December 31, 2014 consisted of the following (in thousands):
		March 31,		December 31,
		2015		2014
	Investment in real estate, net	$	5,764	$	2,507
	Total assets	22,720		24,478
	Total liabilities	6,679		7,467
Impairment of Long-Lived Assets and Long-Lived Assets to be Disposed	Impairment of Long-Lived Assets and Long-Lived Assets to be Disposed
	The Company reviews long-lived assets and certain identifiable intangibles for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The review of recoverability is based on an estimate of the future undiscounted cash flows (excluding interest charges) expected to result from the long-lived asset’s use and eventual disposition. These cash flows consider factors such as expected future operating income, trends and prospects, as well as the effects of leasing demand, competition and other factors. If impairment exists due to the inability to recover the carrying value of a long-lived asset, an impairment loss is recorded to the extent that the carrying value exceeds the estimated fair-value of the property. The Company is required to make subjective assessments as to whether there are impairments in the values of its investments in long-lived assets. These assessments have a direct impact on the Company’s net income because recording an impairment loss results in an immediate negative adjustment to net income. The evaluation of anticipated cash flows is highly subjective and is based in part on assumptions regarding future occupancy, rental rates and capital requirements that could differ materially from actual results in future periods. Although the Company’s strategy is to hold its properties over the long-term, if the Company’s strategy changes or market conditions otherwise dictate an earlier sale date, an impairment loss may be recognized to reduce the property to the lower of the carrying amount or fair-value, and such loss could be material. As of and for the three months ended March 31, 2015, no assets have been identified as impaired and no such impairment losses have been recognized.
Deferred Leasing Costs, Net	Deferred Leasing Costs, Net
	Leasing commissions and other direct costs associated with obtaining new or renewal leases are recorded at cost and amortized on a straight-line basis over the terms of the respective leases, with remaining terms ranging from less than one year to approximately 20 years as of March 31, 2015. Deferred leasing costs also include the net carrying value of acquired in-place leases and acquired management agreements.
	Deferred leasing costs, net at March 31, 2015 consisted of the following (in thousands):
		Balance at			Accumulated
		March 31, 2015			Amortization			Net
	Acquired in-place leases	$	420,032		$	(280,148	)	$	139,884
	Acquired management agreements	25,801			(23,097		)	2,704
	Deferred leasing and other direct costs	119,250			(42,289		)	76,961
		$	565,083		$	(345,534	)	$	219,549
	Deferred leasing costs, net at December 31, 2014 consisted of the following (in thousands):
		Balance at			Accumulated
		December 31, 2014			Amortization			Net
	Acquired in-place leases	$	415,389		$	(271,782	)	$	143,607
	Acquired management agreements	25,801			(22,328		)	3,473
	Deferred leasing and other direct costs	111,290			(38,657		)	72,633
		$	552,480		$	(332,767	)	$	219,713
Investments	Investments
	Investments in equity securities, which are included in other assets on the accompanying consolidated balance sheets, consisted of the following (in thousands):
		March 31,			December 31,
		2015			2014
	Available-for-sale securities, historical cost	$	14,309		$	10,280
	Unrealized gain, net	71,662			48,341
	Available-for-sale securities, fair-value (1)	85,971			58,621
	Privately-held securities, cost basis	43,895			43,428
	Total equity securities	$	129,866		$	102,049
	-1	Determination of fair-value is classified as Level 1 in the fair-value hierarchy based on the use of quoted prices in active markets.
	The Company holds investments in available-for-sale securities of certain publicly-traded companies. Changes in the fair-value of investments classified as available-for-sale are recorded in comprehensive income. The fair-value of the Company's equity investments in publicly-traded companies are based upon the closing trading price of the equity security as of the balance sheet date. Certain of these investments have fair-values less than the Company’s cost basis, net of previous other-than-temporary impairment in these securities due to decreases in their respective stock prices during the three months ended March 31, 2015. However, management has the intent and ability to retain the investments for a period of time sufficient to allow for an anticipated recovery in their market value. Management will continue to periodically evaluate whether any investment, the fair-value of which is less than the Company’s cost basis, should be considered other-than-temporarily impaired. If other-than-temporary impairment is considered to exist, the related unrealized loss will be reclassified from accumulated other comprehensive loss and recorded as a reduction of net income.
	The Company also holds investments in securities of certain privately-held companies and funds, which are recorded at cost basis due to the Company’s lack of control or significant influence over such companies and funds.
	During the three months ended March 31, 2015, the Company recorded impairment charges of $292,000. Impairment charges are included in other expense in the consolidated statements of income and relate to the Company’s investment in a publicly-traded company. Other than this investment, there were no identified events or changes in circumstances that may have a significant adverse effect on the carrying value of the Company’s cost basis investments and therefore, no evaluation of impairment was performed during the three months ended March 31, 2015 on the Company’s remaining cost basis investments.
	In April 2015, the Company received $57.1 million of proceeds from the sale of an investment in a publicly-traded company, resulting in a realized gain on sale of $43.8 million, net of allocation to a noncontrolling interest.
Management's Estimates	Management’s Estimates
	Management has made a number of estimates and assumptions relating to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reporting of revenue and expenses during the reporting period to prepare these consolidated financial statements in conformity with GAAP. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and reported amounts of revenue and expenses that are not readily apparent from other sources. Actual results could differ from those estimates under different assumptions or conditions.

Basis_of_Presentation_and_Summ2

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Schedule of Variable Interest Entities, Wexford	Selected financial data of the VIE at March 31, 2015 and December 31, 2014 consisted of the following (in thousands):
		March 31,			December 31,
		2015			2014
	Investment in real estate, net	$	5,764		$	2,507
	Total assets	22,720			24,478
	Total liabilities	6,679			7,467
Selected Financial Data of the VIEs	Selected financial data of the VIEs at March 31, 2015 and December 31, 2014 consist of the following (in thousands):
		March 31,				December 31,
		2015				2014
	Investment in real estate, net	$	430,343			$	433,842
	Total assets	491,610				493,066
	Total debt	188,780				189,848
	Total liabilities	202,592				203,529
Investments in Real Estate, Net	Investments in real estate, net consisted of the following (in thousands):
		March 31,				December 31,
		2015				2014
	Land	$	643,041			$	704,958
	Land under development	225,846				151,242
	Buildings and improvements	4,909,684				4,877,135
	Construction in progress	738,603				629,679
		6,517,174				6,363,014
	Accumulated depreciation	(999,545		)		(946,439		)
		$	5,517,629			$	5,416,575
Deferred Leasing Costs, Net	Deferred leasing costs, net at March 31, 2015 consisted of the following (in thousands):
		Balance at				Accumulated
		March 31, 2015				Amortization			Net
	Acquired in-place leases	$	420,032			$	(280,148	)	$	139,884
	Acquired management agreements	25,801				(23,097		)	2,704
	Deferred leasing and other direct costs	119,250				(42,289		)	76,961
		$	565,083			$	(345,534	)	$	219,549
	Deferred leasing costs, net at December 31, 2014 consisted of the following (in thousands):
		Balance at				Accumulated
		December 31, 2014				Amortization			Net
	Acquired in-place leases	$	415,389			$	(271,782	)	$	143,607
	Acquired management agreements	25,801				(22,328		)	3,473
	Deferred leasing and other direct costs	111,290				(38,657		)	72,633
		$	552,480			$	(332,767	)	$	219,713
Investments in Equity Securities	Investments in equity securities, which are included in other assets on the accompanying consolidated balance sheets, consisted of the following (in thousands):
		March 31,				December 31,
		2015				2014
	Available-for-sale securities, historical cost	$	14,309			$	10,280
	Unrealized gain, net	71,662				48,341
	Available-for-sale securities, fair-value (1)	85,971				58,621
	Privately-held securities, cost basis	43,895				43,428
	Total equity securities	$	129,866			$	102,049
	-1	Determination of fair-value is classified as Level 1 in the fair-value hierarchy based on the use of quoted prices in active markets.

Equity_of_the_Parent_Company_T

Equity of the Parent Company (Tables)	3 Months Ended
	Mar. 31, 2015
Equity of the Parent Company
Dividends and Distributions	Dividends and Distributions
	The following table lists the dividends and distributions declared by the Parent Company and the Operating Partnership during the three months ended March 31, 2015:
	Declaration Date		Securities Class		Amount Per				Period Covered		Dividend and		Dividend and
					Share/Unit						Distribution		Distribution Amount
											Payable Date
													(In thousands)
	March 16, 2015		Common stock and OP units		$	0.26			January 1, 2015 to March 31, 2015		April 15, 2015		$	54,331
Changes in Accumulated Other Comprehensive Loss by Component	Changes in Accumulated Other Comprehensive Income / (Loss) by Component
	The following table shows the changes in accumulated other comprehensive income / (loss) for the Operating Partnership for the three months ended March 31, 2015, by component (in thousands):
		Foreign currency translation adjustments				Unrealized gains on available- for-sale securities				Gain / (loss) on derivative instruments				Total
	Balance at December 31, 2014	$	2,367			$	38,732			$	(40,221	)		$	878
	Other comprehensive (loss) / income before reclassifications	(1,216		)		35,653				(2,202		)		32,235
	Amounts reclassified from accumulated other comprehensive income (1)	—				(12,334		)		2,502				(9,832		)
	Net other comprehensive (loss) / income	(1,216		)		23,319				300				22,403
	Net other comprehensive income allocable to noncontrolling interest	—				(4,676		)		—				(4,676		)
	Balance as of March 31, 2015	$	1,151			$	57,375			$	(39,921	)		$	18,605
	-1	Amounts reclassified from unrealized gain on available-for-sale securities are included in other income, net in the the consolidated statements of income. Amounts reclassified from loss on derivative instruments are included in interest expense, net in the consolidated statements of income. See Note 9 for further information.
Vested Ownership Interests	The following table shows the vested ownership interests in the Operating Partnership:
		March 31, 2015						December 31, 2014
		Operating Partnership Units and LTIP Units			Percentage of Total			Operating Partnership Units and LTIP Units			Percentage of Total
	BioMed Realty Trust	202,174,206			97.5	%		196,031,538			97.4	%
	Noncontrolling interest consisting of:
	Operating partnership and LTIP units held by employees and related parties	2,645,888			1.3	%		2,645,888			1.3	%
	Operating partnership and LTIP units held by third parties	2,627,145			1.2	%		2,627,145			1.3	%
	Total	207,447,239			100	%		201,304,571			100	%
Parent Company
Equity of the Parent Company
Changes in Accumulated Other Comprehensive Loss by Component	Changes in Accumulated Other Comprehensive Income / (Loss) by Component
	The following table shows the changes in accumulated other comprehensive income / (loss) for the Parent Company for the three months ended March 31, 2015, by component (in thousands):
		Foreign currency translation adjustments				Unrealized gains on available-for-sale securities				Gain / (loss) on derivative instruments				Total
	Balance at December 31, 2014	$	2,309			$	37,705			$	(42,228	)		$	(2,214	)
	Other comprehensive (loss) / income before reclassifications	(1,216		)		35,653				(2,202		)		32,235
	Amounts reclassified from accumulated other comprehensive income (1)	—				(12,334		)		2,502				(9,832		)
	Net other comprehensive (loss) / income	(1,216		)		23,319				300				22,403
	Net other comprehensive loss / (income) allocable to noncontrolling interests	31				(5,408		)		(8		)		(5,385		)
	Balance as of March 31, 2015	$	1,124			$	55,616			$	(41,936	)		$	14,804
	-1	Amounts reclassified from unrealized gain on available-for-sale securities are included in other income, net in the consolidated statements of income. Amounts reclassified from loss on derivative instruments are included in interest expense, net in the consolidated statements of income. See Note 9 for further information.

Capital_of_the_Operating_Partn1

Capital of the Operating Partnership Capital of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2015
Statement of Partners' Capital [Abstract]
Changes in Accumulated Other Comprehensive Loss by Component	Changes in Accumulated Other Comprehensive Income / (Loss) by Component
	The following table shows the changes in accumulated other comprehensive income / (loss) for the Operating Partnership for the three months ended March 31, 2015, by component (in thousands):
		Foreign currency translation adjustments			Unrealized gains on available- for-sale securities			Gain / (loss) on derivative instruments			Total
	Balance at December 31, 2014	$	2,367		$	38,732		$	(40,221	)	$	878
	Other comprehensive (loss) / income before reclassifications	(1,216		)	35,653			(2,202		)	32,235
	Amounts reclassified from accumulated other comprehensive income (1)	—			(12,334		)	2,502			(9,832		)
	Net other comprehensive (loss) / income	(1,216		)	23,319			300			22,403
	Net other comprehensive income allocable to noncontrolling interest	—			(4,676		)	—			(4,676		)
	Balance as of March 31, 2015	$	1,151		$	57,375		$	(39,921	)	$	18,605
	-1	Amounts reclassified from unrealized gain on available-for-sale securities are included in other income, net in the the consolidated statements of income. Amounts reclassified from loss on derivative instruments are included in interest expense, net in the consolidated statements of income. See Note 9 for further information.

Debt_Tables

Debt (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Summary of the Operating Partnership's Outstanding Consolidated Debt	The following is a summary of the Operating Partnership’s outstanding consolidated debt as of March 31, 2015 and December 31, 2014 (dollars in thousands):
		Stated Interest Rate		Effective Interest Rate		Principal Balance
						March 31,			December 31,			Maturity Date
						2015			2014
	Mortgage Notes Payable
	9900 Belward Campus Drive	5.64	%	3.99	%	$	10,447		$	10,486		July 1, 2017
	9901 Belward Campus Drive	5.64	%	3.99	%	12,864			12,913			July 1, 2017
	100 College Street	2.4	%	2.4	%	91,882			82,210			August 2, 2016
	4320 Forest Park Avenue	4	%	2.7	%	21,000			21,000			June 30, 2015
	300 George Street	6.2	%	4.91	%	44,615			45,052			July 1, 2025
	Hershey Center for Applied Research	6.15	%	4.71	%	12,803			12,938			May 5, 2027
	500 Kendall Street (Kendall D)	6.38	%	5.45	%	54,548			55,545			December 1, 2018
	Shady Grove Road	5.97	%	5.97	%	140,599			141,131			September 1, 2016
	University of Maryland BioPark I	5.93	%	4.69	%	15,871			16,056			May 15, 2025
	University of Maryland BioPark II	5.2	%	4.33	%	61,636			61,905			September 5, 2021
	University of Maryland BioPark Garage	5.2	%	4.33	%	4,639			4,660			September 1, 2021
	University of Miami Life Science & Technology Park	4	%	2.89	%	20,000			20,000			February 1, 2016
						490,904			483,896
	Unamortized premiums					12,296			12,861
	Mortgage notes payable, net					503,200			496,757
	Exchangeable Senior Notes (1)	3.75	%	3.75	%	—			95,678			January 30, 2015
	Notes due 2016	3.85	%	3.99	%	400,000			400,000			April 15, 2016
	Notes due 2019	2.63	%	2.72	%	400,000			400,000			May 1, 2019
	Notes due 2020	6.13	%	6.27	%	250,000			250,000			April 15, 2020
	Notes due 2022	4.25	%	4.36	%	250,000			250,000			July 15, 2022
						1,300,000			1,300,000
	Unamortized discounts					(5,745		)	(6,097		)
	Unsecured senior notes, net					1,294,255			1,293,903
	Term Loan due 2017 - U.S. dollar (2)	1.57	%	2.39	%	243,596			243,596			March 30, 2017
	Term Loan due 2017 - GBP (2)	1.9	%	2.14	%	148,030			155,730			March 30, 2017
	Term Loan due 2018	1.36	%	1.67	%	350,000			350,000			March 24, 2018
	Unsecured senior term loans					741,626			749,326
	Unsecured line of credit (3)	1.27	%	1.27	%	226,000			84,000			March 24, 2018
	Total consolidated debt					$	2,765,081		$	2,719,664
	-1	In January 2015, the entire principal amount of the Operating Partnership's Exchangeable Senior Notes due 2030 (the "Exchangeable Senior Notes") was exchanged for 5,764,026 shares of the Parent Company's common stock, at the request of the holders.
	-2	In August 2012, the Operating Partnership converted approximately $156.4 million of outstanding borrowings into British pounds sterling (“GBP”) equal to £100.0 million, which was designated as a net investment hedge to mitigate the risk of fluctuations in foreign currency exchange rates. The principal balance represents the U.S. dollar amount based on the exchange rates of $1.48 to £1.00 and $1.56 to £1.00 at March 31, 2015 and December 31, 2014, respectively. The effective interest rate includes the impact of interest rate swap agreements (see Note 9 for further discussion of interest rate swap agreements).
	-3	At March 31, 2015, the Operating Partnership had additional borrowing capacity under the unsecured line of credit of up to approximately $674.0 million.
Principal Payments Due for Operating Partnership's Consolidated Indebtedness	Maturities of Long-Term Debt
	As of March 31, 2015, principal payments due for the Operating Partnership’s consolidated indebtedness (excluding debt premiums and discounts) were as follows (in thousands):
	2015	$	28,977
	2016	660,291
	2017	423,932
	2018	623,804
	2019	405,724
	Thereafter	615,802
		$	2,758,530

Earnings_Per_Share_of_the_Pare1

Earnings Per Share of the Parent Company (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share, Basic and Diluted [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Computations of basic and diluted earnings per share (in thousands, except share data) were as follows:
		Three Months Ended
		March 31,
		2015			2014
	Basic earnings per share:
	Net income attributable to the Company	$	17,345		$	18,833
	Net income allocable and distributions in excess of earnings to participating securities	(393		)	(378		)
	Net income attributable to common stockholders - basic	$	16,952		$	18,455
	Diluted earnings per share:
	Net income attributable to common stockholders - basic	16,952			18,455
	Net income attributable to noncontrolling interests in Operating Partnership	457			521
	Net income attributable to common stockholders - diluted	$	17,409		$	18,976
	Weighted-average common shares outstanding:
	Basic	200,789,795			190,905,867
	Incremental shares from:
	Performance units	340,879			229,295
	Operating partnership and LTIP units	5,405,474			5,410,374
	Diluted	206,536,148			196,545,536
	Basic and diluted earnings per share:
	Net income per share attributable to common stockholders - basic and diluted	$	0.08		$	0.1

Earnings_Per_Unit_of_the_Opera1

Earnings Per Unit of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2015
Partnership Income [Abstract]
Computations of Basic and Diluted Earnings Per Unit	Computations of basic and diluted earnings per unit (in thousands, except unit data) were as follows:
		Three Months Ended
		March 31,
		2015			2014
	Basic and diluted earnings per unit:
	Net income attributable to the Operating Partnership	$	17,802		$	19,354
	Net income allocable and distributions in excess of earnings to participating securities	(393		)	(378		)
	Net income attributable to unit holders - basic and diluted	$	17,409		$	18,976
	Weighted-average units outstanding:
	Basic	206,195,269			196,316,241
	Incremental units from:
	Performance units	340,879			229,295
	Diluted	206,536,148			196,545,536
	Basic and diluted earnings per unit:
	Net income per unit attributable to unit holders - basic and diluted	$	0.08		$	0.1

Investment_in_Unconsolidated_P1

Investment in Unconsolidated Partnerships (Tables)	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Summary of Unconsolidated Partnerships	The accompanying consolidated financial statements include investments in two limited liability companies with Prudential Real Estate Investors (“PREI”), 10165 McKellar Court, L.P. (“McKellar Court”), a limited partnership with Quidel Corporation, the tenant which occupies the McKellar Court property and BioPark Fremont, LLC ("BioPark Fremont"), a limited liability company with RPC Poppleton, LLC. General information on the PREI limited liability companies, the McKellar Court partnership and BioPark Fremont (each referred to in this footnote individually as a “partnership” and collectively as the “partnerships”) as of March 31, 2015 was as follows:
	Name		Partner		Company’s		Company’s		Date Acquired
					Ownership		Economic
					Interest		Interest
	PREI I LLC (1)		PREI		20%		20%		April 4, 2007
	PREI II LLC		PREI		20%		20%		April 4, 2007
	McKellar Court (2)		Quidel Corporation		22%		22%		September 30, 2004
	BioPark Fremont		RPC Poppleton, LLC		50%		50%		May 31, 2013
	-1	PREI I LLC owns two properties in Cambridge, Massachusetts. At March 31, 2015, there were $139.0 million in outstanding borrowings on a secured loan facility held by a wholly-owned subsidiary of PREI I LLC, with a contractual interest rate of 2.23% (including the applicable credit spread) and a maturity date of August 13, 2015 (with an option to extend the maturity date to August 13, 2016 at its discretion after satisfying certain conditions and paying an extension fee).
	-2	The Company’s investment in the McKellar Court partnership (maximum exposure to losses) was approximately $11.8 million at March 31, 2015. The Company’s economic interest in the McKellar Court partnership entitles it to 75% of the extraordinary cash flows after repayment of the partners’ capital contributions and 22% of the operating cash flows.
Summary of Selected Balance Sheet Information	The condensed combined balance sheets for all of the Company’s unconsolidated partnerships were as follows (in thousands):
		March 31,				December 31,
		2015				2014
	Assets:
	Investments in real estate, net	$	262,727			$	267,007
	Cash and cash equivalents (including restricted cash)	8,504				6,057
	Other assets	11,445				11,599
	Total assets	$	282,676			$	284,663
	Liabilities and members’ equity:
	Mortgage notes payable and secured loan	$	152,077			$	152,056
	Other liabilities	8,449				9,020
	Members’ equity	122,150				123,587
	Total liabilities and members' equity	$	282,676			$	284,663
	Company’s investments in unconsolidated partnerships	$	34,978			$	35,291
Schedule of Selected Income Statement Information	The selected data and results of operations for the unconsolidated partnerships were as follows (in thousands):
			Three Months Ended
			March 31,
			2015				2014
	Total revenues		$	8,728			$	4,059
	Total expenses		(9,086		)		(6,130		)
	Net loss		$	(358	)		$	(2,071	)
	Company’s equity in net income / (loss) of unconsolidated partnerships		$	153			$	(138	)
	Fees earned by the Company (1)		$	111			$	283
	-1	The Company acts as the operating member or partner, as applicable, and day-to-day manager for the partnerships. The Company is entitled to receive fees for providing construction and development services (as applicable) and management services to the PREI joint ventures, which are reflected in tenant recoveries and other income in the consolidated statements of income.

Derivatives_and_Other_Financia1

Derivatives and Other Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Derivative Instruments	The following is a summary of the terms of the interest rate swaps and their respective fair-values (dollars in thousands):
											Fair-Value(1)
		Notional Amount									March 31,			December 31,
						Strike Rate			Effective Date	Expiration Date	2015			2014
	Interest rate swaps	$	200,000			1.163	%		March 30, 2012	March 30, 2017	$	(1,960	)	$	(1,448	)
	Interest rate swaps	200,000				0.701	%		October 1, 2013	October 1, 2016	(569		)	(186		)
	Interest rate swaps(2)	74,015				0.731	%		August 2, 2012	March 30, 2017	59			63
	Interest rate swaps(2)	74,015				0.7425	%		August 2, 2012	March 30, 2017	43			45
	Total interest rate swaps	$	548,030								$	(2,427	)	$	(1,526	)
	-1	Fair-value of derivative instruments does not include any related accrued interest payable, which is included in accrued expenses on the accompanying consolidated balance sheets. Derivative valuations are classified in Level 2 of the fair-value hierarchy. Assets are included in other assets and liabilities are included in accounts payable, accrued expenses and other liabilities on the accompanying consolidated balance sheets.
	-2	Translation to U.S. dollars is based on exchange rates of $1.48 to £1.00 and $1.56 to £1.00 at March 31, 2015 and December 31, 2014, respectively.
Summary of Derivative Instruments, Effect on OCI	The following is a summary of the amount of gain / (loss) recognized in other comprehensive income related to the derivative instruments (in thousands):
			Three Months Ended
			March 31,
			2015				2014
	Amount of loss recognized in other comprehensive income (effective portion):
	Cash flow hedges
	Interest rate swaps		$	(2,202	)		$	(1,449	)
	Amount of (loss) / income reclassified from accumulated other comprehensive loss to income (effective portion):
	Cash flow hedges
	Interest rate swaps (1)		$	(839	)		$	859
	Forward starting swaps (2)		(1,663		)		1,691
	Total interest rate swaps		$	(2,502	)		$	2,550
	Amount of (loss) / gain recognized in income (ineffective portion and amount excluded from effectiveness testing):
	Other derivative instruments		(170		)		162
	Total (loss) / gain on derivative instruments		$	(170	)		$	162
	-1	Amount represents payments made to swap counterparties for the effective portion of interest rate swaps that were recognized as an increase to interest expense for the periods presented (the amount was recorded as an increase and corresponding decrease to accumulated other comprehensive loss in the same accounting period).
	-2	Amount represents reclassifications of deferred interest costs from accumulated other comprehensive loss to interest expense related to the Company’s previously settled forward starting swaps.

FairValue_of_Financial_Instrum1

Fair-Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair-Value and Carrying Value of the Company's Financial Instruments	At March 31, 2015 and December 31, 2014, the aggregate fair-value and the carrying value of the Company’s financial instruments were as follows (in thousands):
		March 31, 2015				December 31, 2014
		Fair-Value (1)		Carrying Value		Fair-Value (1)		Carrying Value
	Mortgage notes payable, net	$	508,782	$	503,200	$	502,115	$	496,757
	Exchangeable Senior Notes	—		—		134,619		95,678
	Notes due 2016, net	409,600		399,435		411,600		399,304
	Notes due 2019, net	402,100		397,984		398,280		397,873
	Notes due 2020, net	285,250		248,512		283,250		248,450
	Notes due 2022, net	260,000		248,324		258,250		248,275
	Term Loan due 2017 - U.S. dollar	244,797		243,596		244,945		243,596
	Term Loan due 2017 - GBP (2)	148,758		148,030		156,589		155,730
	Term Loan due 2018	350,515		350,000		350,557		350,000
	Unsecured line of credit	225,668		226,000		83,866		84,000
	Derivative instruments (3)	2,203		2,203		1,132		1,132
	Available-for-sale securities	85,971		85,971		58,621		58,621
	-1	Fair-values of debt and derivative instruments are classified in Level 2 of the fair-value hierarchy. Fair-value of available-for-sale securities are classified in Level 1 of the fair-value hierarchy.
	-2	The principal balance represents the U.S. dollar amount based on the exchange rate of $1.48 to £1.00 and $1.56 to £1.00 at March 31, 2015 and December 31, 2014, respectively.
	-3	The Company’s derivative instruments are reflected in other assets and in accounts payable, accrued expenses and other liabilities on the accompanying consolidated balance sheets based on their respective balances (see Note 9).

Acquisitions_Tables

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2015
Business Acquisition
Schedule of Purchase Price Allocation	Acquisitions
	The Company acquired one property during the three months ended March 31, 2015. The table below reflects the preliminary purchase price allocation for this acquisition (in thousands).
	Property	Acquisition Date	Investments in Real Estate		Below Market Lease			In-Place Lease		Acquisition Date Fair-Value
	307 Westlake	February 11, 2015	$	85,733	$	(1,824	)	$	5,791	$	89,700
	Weighted average intangible amortization life (in months)				96			95
	Revenues of approximately $1.0 million and net income of $191,183 associated with the 307 Westlake property are included in the consolidated statements of income for the three months ended March 31, 2015 for both the Parent Company and the Operating Partnership.

Organization_of_the_Parent_Com1

Organization of the Parent Company and Description of Business (Details)	Mar. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements
Equity Method Investment, Ownership Percentage	100.00%	100.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	2.50%
Parent Company
Organization, Consolidation and Presentation of Financial Statements
Equity Method Investment, Ownership Percentage	97.50%	97.40%

Basis_of_Presentation_and_Summ3

Basis of Presentation and Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended	1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Apr. 29, 2015
	VIEs		sqft
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Deferred Costs and Other Assets	$5,200,000
Tax credits, net of costs and estimated put paments		15,500,000
Tax Credits Delivered		-12,800,000
Real Estate Investment Property, Net	5,517,629,000		5,416,575,000
Number of Variable Interest Entities that the Company is the Primary Beneficiary	6
Reclassification Of Other Than Temporary Unrealized Loss From Accumulated Other Comprehensive Income To General And Administrative Expense	-292,000
Extension options	1 year
Lease Termination Revenue	16,200,000	5,500,000
Finite-Lived Intangible Assets, Net	219,549,000		219,713,000
Foreign
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Revenue from properties outside the United States, net	4,200,000	4,800,000
Percentage of Company's total revenue	2.40%	2.80%
Real Estate Investment Property, Net	203,700,000		200,200,000
Boston Development Project
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
BioMed Realty Trust Interest in Construction Loan			255,000,000
Construction Loan			355,000,000
Square Footage of Real Estate Property			1,100,000
Percent Leased			95.00%
Investment In Construction Loan			191,200,000
Deferred Leasing and Other Direct Costs [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Finite-Lived Intangible Assets, Net	76,961,000		72,633,000
Historic and New Market Tax Credits [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Syndicated Historic Tax Credits and New Market Tax Credits	10
New Market Tax Credits [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Percentage Of Tax Credit Recapture	100.00%
Historical Tax Credit Recapture Period	1 year
Historic tax credit [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Percentage Of Qualified Investments	39.00%
Percentage Of Tax Credit Recapture	20.00%
Maximum [Member] | Deferred Leasing and Other Direct Costs [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	20 years
Parent Company
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Provision for Doubtful Accounts	297,000	526,000
Revenue from properties outside the United States, net	178,010,000	168,876,000
Real Estate Investment Property, Net	5,517,629,000		5,416,575,000
Proceeds from the sale of debt and equity securities	13,696,000	13,952,000
Marketable Securities, Realized Gain (Loss)	-12,334,000
Other revenue	16,534,000	10,115,000
Subsequent Event [Member]
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Proceeds from the sale of debt and equity securities				57,100,000
Marketable Securities, Realized Gain (Loss)				$43,800,000

Basis_of_Presentation_and_Summ4

Basis of Presentation and Summary of Significant Accounting Policies (Selected Financial Data of the VIEs) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Accounting Policies [Abstract]
Variable Interest Entity Carrying Amount Of Collateralized Investment In Real Estate Net	$430,343	$433,842
Variable Interest Entity, Consolidated, Carrying Amount, Assets	491,610	493,066
Total Debt	188,780	189,848
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	202,592	203,529
Wexford Merger [Member]
Accounting Policies [Abstract]
Variable Interest Entity Carrying Amount Of Collateralized Investment In Real Estate Net	5,764	2,507
Variable Interest Entity, Consolidated, Carrying Amount, Assets	22,720	24,478
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$6,679	$7,467

Basis_of_Presentation_and_Summ5

Basis of Presentation and Summary of Significant Accounting Policies (Investments in Real Estate, Net) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Accounting Policies [Abstract]
Land	$643,041	$704,958
Land Under Development	225,846	151,242
Buildings and Improvements	4,909,684	4,877,135
Construction in Progress	738,603	629,679
Real Estate Investment Property, at Cost	6,517,174	6,363,014
Accumulated Depreciation	-999,545	-946,439
Real Estate Investment Property, Net	$5,517,629	$5,416,575

Basis_of_Presentation_and_Summ6

Basis of Presentation and Summary of Significant Accounting Policies (Deferred Leasing Costs, Net) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Deferred Leasing Costs
Finite-Lived Intangible Assets, Gross	$565,083	$552,480
Finite-Lived Intangible Assets, Accumulated Amortization	-345,534	-332,767
Finite-Lived Intangible Assets, Net	219,549	219,713
Leases, Acquired-in-Place [Member]
Deferred Leasing Costs
Finite-Lived Intangible Assets, Gross	420,032	415,389
Finite-Lived Intangible Assets, Accumulated Amortization	-280,148	-271,782
Finite-Lived Intangible Assets, Net	139,884	143,607
Acquired Management Agreements
Deferred Leasing Costs
Finite-Lived Intangible Assets, Gross	25,801	25,801
Finite-Lived Intangible Assets, Accumulated Amortization	-23,097	-22,328
Finite-Lived Intangible Assets, Net	2,704	3,473
Deferred Leasing and Other Direct Costs [Member]
Deferred Leasing Costs
Finite-Lived Intangible Assets, Gross	119,250	111,290
Finite-Lived Intangible Assets, Accumulated Amortization	-42,289	-38,657
Finite-Lived Intangible Assets, Net	$76,961	$72,633

Basis_of_Presentation_and_Summ7

Basis of Presentation and Summary of Significant Accounting Policies (Deferred Leasing Costs-Estimated Amortization) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Finite-Lived Intangible Assets, Net	$219,549	$219,713

Basis_of_Presentation_and_Summ8

Basis of Presentation and Summary of Significant Accounting Policies (Revenue Recognition-Estimated Amortization) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Finite-Lived Intangible Assets, Net	$219,549	$219,713

Basis_of_Presentation_and_Summ9

Basis of Presentation and Summary of Significant Accounting Policies (Investments) (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Accounting Policies [Abstract]
Available-for-sale securities, historical cost	$14,309		$10,280
Unrealized gain, net	71,662		48,341
Available-for-sale securities, fair-value	85,971	[1]	58,621	[1]
Privately-held securities, cost basis	43,895		43,428
Total equity securities	$129,866		$102,049
[1]	Determination of fair-value is classified as Level 1 in the fair-value hierarchy based on the use of quoted prices in active markets.

Recovered_Sheet1

Basis of Presentation and Summary of Significant Accounting Policies Selected Financial Data of the VIEs, Wexford (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Variable Interest Entity Carrying Amount Of Collateralized Investment In Real Estate Net	$430,343	$433,842
Variable Interest Entity, Consolidated, Carrying Amount, Assets	491,610	493,066
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	202,592	203,529
Wexford Merger [Member]
Variable Interest Entity Carrying Amount Of Collateralized Investment In Real Estate Net	5,764	2,507
Variable Interest Entity, Consolidated, Carrying Amount, Assets	22,720	24,478
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$6,679	$7,467

Equity_of_the_Parent_Company_N

Equity of the Parent Company (Narrative) (Details) (Parent Company, USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2014	Mar. 31, 2013	Mar. 31, 2014	Dec. 31, 2014
Equity of the Parent Company
Shares surrendered to the Company and retired in lieu of cash payments for taxes due on the vesting of restricted stock	-237,789
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$5.40
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	3.8
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	2 years 9 months
Noncontrolling Interest Redemption Value	$122.70
Average Closing Price Per Common Share		$22.69
Noncontrolling Interest Redemption Value Calculation Days		10 days
Common Stock
Equity of the Parent Company
Common Stock, Shares Outstanding	203,563,054				197,442,432
Operating Partnership Units and LTIP Units
Equity of the Parent Company
Partnership Units, Shares Outstanding	5,083,400
LTIP Units, Shares Outstanding	322,074
Restricted Stock Issued to Employees
Equity of the Parent Company
Restricted Stock Awards Issued	586,674
Performance Shares 2012 [Member]
Equity of the Parent Company
Performance units			136,296
Performance Shares 2013 [Member]
Equity of the Parent Company
Shares surrendered to the Company and retired in lieu of cash payments for taxes due on the vesting of restricted stock	-5,504
Performance units forfeited during the period	-189,929
Performance units				203,144
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	13,215
Performance Shares
Equity of the Parent Company
Performance units	370,880

Equity_of_the_Parent_Company_D

Equity of the Parent Company (Dividends and Distributions) (Details) (Common Stock And Op Units [Member], USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014
Common Stock And Op Units [Member]
Equity of the Parent Company
Common Stock, Dividends, Per Share, Declared	$0.26
Dividends Payable, Date to be Paid	15-Apr-15
Payments of Dividends	$54,331
Dividends Payable, Date Declared	16-Mar-15

Equity_of_the_Parent_Company_C

Equity of the Parent Company (Changes in Accumulated Other Comprehensive Loss by Component) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), Net of Tax	$22,403
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	-5,385
Parent Company
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, net	14,804			-2,214
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	32,235
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-9,832	[1]
Other Comprehensive Income (Loss), Net of Tax	22,403		16,651
Accumulated Translation Adjustment [Member] | Parent Company
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, net	1,124			2,309
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	-1,216
Other Comprehensive Income (Loss), Net of Tax	-1,216
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	31
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Parent Company
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, net	55,616			37,705
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	35,653
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-12,334
Other Comprehensive Income (Loss), Net of Tax	23,319
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	-5,408
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Parent Company
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, net	-41,936			-42,228
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,502
Other Comprehensive Income (Loss), Net of Tax	300
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	-8
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Interest Rate Swaps | Parent Company
Accumulated Other Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	($2,202)
[1]	Amounts reclassified from unrealized gain on available-for-sale securities are included in other income, net in the consolidated statements of income. Amounts reclassified from loss on derivative instruments are included in interest expense, net in the consolidated statements of income. See Note 9 for further information.

Equity_of_the_Parent_Company_V

Equity of the Parent Company (Vested Ownership Interests) (Details)	Mar. 31, 2015	Dec. 31, 2014
Equity of the Parent Company
Operating Partnership Units and LTIP Units	207,447,239	201,304,571
Equity Method Investment, Ownership Percentage	100.00%	100.00%
Parent Company
Equity of the Parent Company
Operating Partnership Units and LTIP Units	202,174,206	196,031,538
Equity Method Investment, Ownership Percentage	97.50%	97.40%
Operating Partnership and LTIP Units Held By Employees and Related Parties
Equity of the Parent Company
Operating Partnership Units and LTIP Units	2,645,888	2,645,888
Equity Method Investment, Ownership Percentage	1.30%	1.30%
Operating Partnership and LTIP Units Held By Third Parties
Equity of the Parent Company
Operating Partnership Units and LTIP Units	2,627,145	2,627,145
Equity Method Investment, Ownership Percentage	1.20%	1.30%

Capital_of_the_Operating_Partn2

Capital of the Operating Partnership (Narrative) (Details) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2015	Dec. 31, 2014
Capital of the Operating Partnership [Line Items]
Equity Method Investment, Ownership Percentage		100.00%	100.00%
BIOMED REALTY, L.P.
Capital of the Operating Partnership [Line Items]
Partners' Capital Account, Units		208,646,454
LTIP Units, Shares Outstanding		322,074
Parent Company
Capital of the Operating Partnership [Line Items]
Noncontrolling Interest Redemption Value		122.7
Average Closing Price Per Common Share	$22.69
Noncontrolling Interest Redemption Value Calculation Days	10 days
Parent Company
Capital of the Operating Partnership [Line Items]
Equity Method Investment, Ownership Percentage		97.50%	97.40%

Capital_of_the_Operating_Partn3

Capital of the Operating Partnership (Changes in Accumulated Other Comprehensive Loss by Component) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Capital of the Operating Partnership [Line Items]
Other Comprehensive Income (Loss), Net of Tax	$22,403
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	-5,385
BIOMED REALTY, L.P.
Capital of the Operating Partnership [Line Items]
Net Income (Loss) Allocated to Limited Partners	17,802		19,354
Accumulated other comprehensive loss, net	18,605			878
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	32,235
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-9,832	[1]
Other Comprehensive Income (Loss), Net of Tax	22,403		16,651
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	-4,676
Accumulated Translation Adjustment [Member] | BIOMED REALTY, L.P.
Capital of the Operating Partnership [Line Items]
Accumulated other comprehensive loss, net	1,151			2,367
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	-1,216
Other Comprehensive Income (Loss), Net of Tax	-1,216
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0
Accumulated Net Unrealized Investment Gain (Loss) [Member] | BIOMED REALTY, L.P.
Capital of the Operating Partnership [Line Items]
Accumulated other comprehensive loss, net	57,375			38,732
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	35,653
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-12,334
Other Comprehensive Income (Loss), Net of Tax	23,319
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	-4,676
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | BIOMED REALTY, L.P.
Capital of the Operating Partnership [Line Items]
Accumulated other comprehensive loss, net	-39,921			-40,221
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	-2,202
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,502
Other Comprehensive Income (Loss), Net of Tax	300
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	$0
[1]	Amounts reclassified from unrealized gain on available-for-sale securities are included in other income, net in the consolidated statements of income. Amounts reclassified from loss on derivative instruments are included in interest expense, net in the consolidated statements of income. See Note 9 for further information.

Debt_Debt_Narrative_Details

Debt Debt (Narrative) (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Debt Instruments
Principal Balance	$2,758,530
Interest Rate Swaps
Debt Instruments
Derivative, Notional Amount	548,030
Interest Rate Swaps | Interest Rate Swaps - $200M (2)
Debt Instruments
Derivative, Inception Date	1-Oct-13
Derivative, Notional Amount	200,000
Derivative, Fixed Interest Rate	0.70%
Exchangeable Senior Notes
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Tender Offer Redemption Date	30-Jan-15
Mortgage Notes Payable
Debt Instruments
Principal Balance	490,904		483,896
Unsecured Line of Credit
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	1.27%	[1]
Debt Instrument, Maturity Date	24-Mar-18	[1]
Unsecured Term Loans
Debt Instruments
Unsecured Term Loans	741,626		749,326
Unsecured Term Loan GBP Portion [Member]
Debt Instruments
Foreign Currency Exchange Rate, Translation	1.48		1.56
Unsecured Term Loan GBP Portion [Member] | Unsecured Term Loans
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	1.90%	[2]
Debt Instrument, Maturity Date	30-Mar-17	[2]
Unsecured Term Loans	148,030	[2]	155,730	[2]
Unsecured Term Loan Due 2018 [Member] | Unsecured Term Loans
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	1.36%	[1]
Debt Instrument, Maturity Date	24-Mar-18	[1]
Unsecured Term Loans	350,000	[1]	350,000	[1]
Unsecured Term Loan USD Portion [Member] | Unsecured Term Loans
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	1.57%	[2]
Debt Instrument, Maturity Date	30-Mar-17	[2]
Unsecured Term Loans	243,596	[2]	243,596	[2]
Unsecured Senior Notes Due Twenty Nineteen [Member] | Unsecured Debt [Member]
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	2.63%
Debt Instrument, Maturity Date	1-May-19
Unsecured Senior Notes Due Twenty Twenty [Member] | Unsecured Debt [Member]
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	6.13%
Debt Instrument, Maturity Date	15-Apr-20
Unsecured Senior Notes Due Twenty Twenty-Two [Member] | Unsecured Debt [Member]
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	4.25%
Debt Instrument, Maturity Date	15-Jul-22
Unsecured Senior Notes Due Twenty Sixteen [Member] | Unsecured Debt [Member]
Debt Instruments
Debt Instrument, Interest Rate, Stated Percentage	3.85%
Debt Instrument, Maturity Date	15-Apr-16
Parent Company
Debt Instruments
Stock Issued During Period, Shares, Conversion of Convertible Securities	5,764,026
Stock Issued During Period, Value, Conversion of Convertible Securities	$95,678
[1]	At MarchB 31, 2015, the Operating Partnership had additional borrowing capacity under the unsecured line of credit of up to approximately $674.0 million
[2]	In January 2015, the entire principal amount of the Operating Partnership's Exchangeable Senior Notes due 2030 (the "Exchangeable Senior Notes") was exchanged for 5,764,026 shares of the Parent Company's common stock, at the request of the holders.

Debt_Summary_of_the_Operating_

Debt (Summary of the Operating Partnership's Outstanding Consolidated Debt) (Details)

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Dec. 31, 2014

USD ($)

USD ($)

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Mortgage Notes Payable

Exchangeable Senior Notes

Exchangeable Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Senior Notes

Unsecured Term Loans

Unsecured Term Loans

Unsecured Line of Credit

Unsecured Line of Credit

Unsecured Line of Credit and Term Loan

Unsecured Term Loan USD Portion [Member]

Unsecured Term Loan USD Portion [Member]

Unsecured Term Loan GBP Portion [Member]

Unsecured Term Loan GBP Portion [Member]

Unsecured Term Loan GBP Portion [Member]

Unsecured Term Loan GBP Portion [Member]

Unsecured Term Loan GBP Portion [Member]

Unsecured Term Loan GBP Portion [Member]

Unsecured Term Loan Due 2018 [Member]

Unsecured Term Loan Due 2018 [Member]

USD ($)

USD ($)

9900 Belward Campus Drive

9900 Belward Campus Drive

9901 Belward Campus Drive

9901 Belward Campus Drive

100 College Street [Member]

100 College Street [Member]

4320 Forest Park Avenue

4320 Forest Park Avenue

300 George Street [Member]

300 George Street [Member]

Hershey Center for Applied Research

Hershey Center for Applied Research

500 Kendall Street (Kendall D)

500 Kendall Street (Kendall D)

Shady Grove Road

Shady Grove Road

University of Maryland BioPark I

University of Maryland BioPark I

University of Maryland BioPark II

University of Maryland BioPark II

University of Maryland BioPark Garage

University of Maryland BioPark Garage

University of Miami Life Science & Technology Park

University of Miami Life Science & Technology Park

USD ($)

USD ($)

USD ($)

Unsecured Senior Notes Due Twenty Sixteen [Member]

Unsecured Senior Notes Due Twenty Sixteen [Member]

Unsecured Senior Notes Due Twenty Nineteen [Member]

Unsecured Senior Notes Due Twenty Nineteen [Member]

Unsecured Senior Notes Due Twenty Twenty [Member]

Unsecured Senior Notes Due Twenty Twenty [Member]

Unsecured Senior Notes Due Twenty Twenty-Two [Member]

Unsecured Senior Notes Due Twenty Twenty-Two [Member]

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Unsecured Term Loans

Unsecured Term Loans

Unsecured Term Loans

Unsecured Term Loans

Unsecured Term Loans

Unsecured Term Loans

Unsecured Term Loans

Unsecured Term Loans

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD

GBP

USD ($)

USD ($)

USD ($)

GBP (£)

Debt Instruments

Stated Interest Rate

5.64%

5.64%

2.40%

4.00%

[1]

6.20%

6.15%

[1]

6.38%

5.97%

5.93%

[1]

5.20%

[1]

5.20%

[1]

4.00%

[1]

3.75%

3.85%

2.63%

6.13%

4.25%

1.27%

[2]

1.57%

[3]

1.90%

[3]

1.36%

[2]

Effective Interest Rate

3.99%

3.99%

2.40%

2.70%

[1]

4.91%

4.71%

[1]

5.45%

5.97%

4.69%

[1]

4.33%

[1]

4.33%

[1]

2.89%

[1]

3.75%

3.99%

2.72%

6.27%

4.36%

1.27%

[2]

2.39%

[3]

2.14%

[3]

1.67%

[2]

Principal Balance

$2,758,530,000

$490,904,000

$483,896,000

$10,447,000

$10,486,000

$12,864,000

$12,913,000

$91,882,000

$82,210,000

$21,000,000

[1]

$21,000,000

[1]

$44,615,000

$45,052,000

$12,803,000

[1]

$12,938,000

[1]

$54,548,000

$55,545,000

$140,599,000

$141,131,000

$15,871,000

[1]

$16,056,000

[1]

$61,636,000

[1]

$61,905,000

[1]

$4,639,000

[1]

$4,660,000

[1]

$20,000,000

[1]

$20,000,000

[1]

Unamortized Premiums

12,296,000

12,861,000

Mortgage Notes Payable, net

503,200,000

496,757,000

Exchangeable Senior Notes

95,678,000

Tender Offer Redemption Date

30-Jan-15

Unsecured Senior Notes

1,300,000,000

1,300,000,000

400,000,000

400,000,000

400,000,000

400,000,000

250,000,000

250,000,000

250,000,000

250,000,000

Unamortized Discounts

-5,745,000

-6,097,000

Unsecured Senior Notes, net

1,294,255,000

1,293,903,000

Unsecured Term Loans

741,626,000

749,326,000

243,596,000

[3]

243,596,000

[3]

148,030,000

[3]

155,730,000

[3]

156,400,000

[3]

100,000,000

[3]

350,000,000

[2]

350,000,000

[2]

Unsecured Line of Credit

226,000,000

[2]

84,000,000

[2]

Total Consolidated Debt

2,765,081,000

2,719,664,000

Maturity Date

1-Jul-17

1-Jul-17

2-Aug-16

30-Jun-15

[1]

1-Jul-25

5-May-27

[1]

1-Dec-18

1-Sep-16

15-May-25

[1]

5-Sep-21

[1]

1-Sep-21

[1]

1-Feb-16

[1]

15-Apr-16

1-May-19

15-Apr-20

15-Jul-22

24-Mar-18

[2]

30-Mar-17

[3]

30-Mar-17

[3]

24-Mar-18

[2]

Foreign Currency Exchange Rate, Translation

1.48

1.56

LOC Remaining Borrowing Capacity

$674,000,000

[1]

In August 2012, the Operating Partnership converted approximately $156.4 million of outstanding borrowings into British pounds sterling (bGBPb) equal to £100.0 million, which was designated as a net investment hedge to mitigate the risk of fluctuations in foreign currency exchange rates. The principal balance represents the U.S. dollar amount based on the exchange rates of $1.48 to £1.00 and $1.56 to £1.00 at MarchB 31, 2015 and DecemberB 31, 2014, respectively. The effective interest rate includes the impact of interest rate swap agreements (see Note 9 for further discussion of interest rate swap agreements).

[2]

At MarchB 31, 2015, the Operating Partnership had additional borrowing capacity under the unsecured line of credit of up to approximately $674.0 million

[3]

In January 2015, the entire principal amount of the Operating Partnership's Exchangeable Senior Notes due 2030 (the "Exchangeable Senior Notes") was exchanged for 5,764,026 shares of the Parent Company's common stock, at the request of the holders.

Debt_Principal_Payments_Due_fo

Debt (Principal Payments Due for Operating Partnership's Consolidated Indebtedness) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Year 1	$28,977
Year 2	660,291
Year 3	423,932
Year 4	623,804
Year 5	405,724
Thereafter	615,802
Principal Balance	2,758,530
Exchangeable Senior Notes
Exchangeable Senior Notes		$95,678

Earnings_Per_Share_of_the_Pare2

Earnings Per Share of the Parent Company (Narrative) (Details) (Parent Company)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Parent Company
Antidilutive Securities Excluded from Computation of Earnings Per Share
Exchangeable Senior Notes Due 2030	1,194,015	10,525,410

Earnings_Per_Share_of_the_Pare3

Earnings Per Share of the Parent Company (Schedule of Earnings Per Share, Basic and Diluted) (Details) (Parent Company, USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Parent Company
Schedule of Earnings Per Share Basic and Diluted
Net Income (Loss) Attributable to Parent	$17,345	$18,833
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic	-393	-378
Net Income (Loss) Available to Common Stockholders, Basic	16,952	18,455
Income (Loss) from Continuing Operations Attributable to Parent	16,952	18,455
Income (loss) from continuing operations attributable to noncontrollinginterests diluted	457	521
Net Income (Loss) Available to Common Stockholders, Diluted	$17,409	$18,976
Weighted Average Number of Shares Outstanding, Basic	200,789,795	190,905,867
Amount of Dilutive Securities Performance Units	340,879	229,295
Amount Of Dilutive Securities Operating Partnership And Ltip Units	5,405,474	5,410,374
Basic and Diluted	206,536,148	196,545,536
Earnings Per Share, Basic and Diluted	$0.08	$0.10

Earnings_Per_Unit_of_the_Opera2

Earnings Per Unit of the Operating Partnership Earnings Per Unit of the Operating Partnership (Narrative) (Details) (BIOMED REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
BIOMED REALTY, L.P.
Antidilutive Securities Excluded from Computation of Earnings Per Share
Exchangeable Senior Notes Due 2030	1,194,015	10,525,410

Earnings_Per_Unit_of_the_Opera3

Earnings Per Unit of the Operating Partnership (Computations of Basic and Diluted Earnings Per Unit) (Details) (BIOMED REALTY, L.P., USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
BIOMED REALTY, L.P.
Earnings Per Unit of the Operating Partnership
Net Income (Loss) Allocated to Limited Partners	$17,802	$19,354
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic	-393	-378
Net Income (Loss) Available to Common Stockholders, Diluted	$17,409	$18,976
Weighted Average Number of Shares Outstanding, Basic	206,195,269	196,316,241
Amount of Dilutive Securities Performance Units	340,879	229,295
Basic and Diluted	206,536,148	196,545,536
Net Income per Unit Attributable to Unitholders, Basic and Diluted	$0.08	$0.10
Earnings Per Share, Diluted	$0.08

Investment_in_Unconsolidated_P2

Investment in Unconsolidated Partnerships (Narrative) (Details)	Mar. 31, 2015
	PREI_LLCs
Equity Method Investments and Joint Ventures [Abstract]
Number of Investments in Limited Liability Companies	2

Investment_in_Unconsolidated_P3

Investment in Unconsolidated Partnerships (Summary of Unconsolidated Partnerships) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Sep. 30, 2014		Dec. 31, 2014
	properties
Investment In Unconsolidated Partnerships
Equity Method Investment, Ownership Percentage	100.00%				100.00%
PREI I LLC
Investment In Unconsolidated Partnerships
Equity Method Investment, Ownership Percentage	20.00%	[1]
Company's Economic Interest	20.00%	[1]
Date Acquired			4-Apr-07	[1]
Number Of Properties In Portfolio Of Prei I Llc	2
Unsecured line of credit	$139,000,000
Line Of Credit Facility Weighted Average Interest Rate	2.23%
Line of Credit Facility, Expiration Date	13-Aug-15
PREI II LLC
Investment In Unconsolidated Partnerships
Equity Method Investment, Ownership Percentage	20.00%
Company's Economic Interest	20.00%
Date Acquired			4-Apr-07
McKellar Court
Investment In Unconsolidated Partnerships
Equity Method Investment, Ownership Percentage	22.00%	[2]
Company's Economic Interest	22.00%	[2]
Date Acquired			30-Sep-04	[2]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$11,800,000
Percent Of Extraordinary Cash Flow Entitled From Variable Interest Entity	75.00%
Percent Of Operating Cash Flows Entitled From Variable Interest Entity	22.00%
BioPark Fremont
Investment In Unconsolidated Partnerships
Equity Method Investment, Ownership Percentage	50.00%
Company's Economic Interest	50.00%
Date Acquired			31-May-13
[1]	PREI I LLC owns two properties in Cambridge, Massachusetts. At MarchB 31, 2015, there were $139.0 million in outstanding borrowings on a secured loan facility held by a wholly-owned subsidiary of PREI I LLC, with a contractual interest rate of 2.23% (including the applicable credit spread) and a maturity date of AugustB 13, 2015 (with an option to extend the maturity date to August 13, 2016 at its discretion after satisfying certain conditions and paying an extension fee).
[2]	The Companybs investment in the McKellar Court partnership (maximum exposure to losses) was approximately $11.8 million at MarchB 31, 2015. The Companybs economic interest in the McKellar Court partnership entitles it to 75% of the extraordinary cash flows after repayment of the partnersb capital contributions and 22% of the operating cash flows.

Investment_in_Unconsolidated_P4

Investment in Unconsolidated Partnerships (Summary of Selected Balance Sheet Information) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Equity Method Investments and Joint Ventures [Abstract]
Investments in real estate, net	$262,727	$267,007
Cash and cash equivalents (including restricted cash)	8,504	6,057
Other assets	11,445	11,599
Total assets	282,676	284,663
Mortgage notes payable and secured loan	152,077	152,056
Other liabilities	8,449	9,020
Members' equity	122,150	123,587
Total liabilities and equity	282,676	284,663
Company's net investment in unconsolidated partnerships	$34,978	$35,291

Investment_in_Unconsolidated_P5

Investment in Unconsolidated Partnerships (Summary of Selected Income Statement Information) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Total revenues	$8,728		$4,059
Total expenses	-9,086		-6,130
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	-358		-2,071
Company's equity in net loss of unconsolidated partnerships	153		-138
Fees earned by the Company	$111	[1]	$283
[1]	The Company acts as the operating member or partner, as applicable, and day-to-day manager for the partnerships. The Company is entitled to receive fees for providing construction and development services (as applicable) and management services to the PREI joint ventures, which are reflected in tenant recoveries and other income in the consolidated statements of income.

Derivatives_and_Other_Financia2

Derivatives and Other Financial Instruments (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Derivative
Derivative, Gain (Loss) on Derivative, Net	($170,000)	$162,000
Derivative, Deferred Interest Costs Amortization Period	4 years
Interest Rate Swaps
Derivative
Derivative, Notional Amount	548,030,000
Forward Starting Swaps
Derivative
Derivative, Deferred Interest Costs	27,000,000
Derivative, Lower Remaining Maturity Range	10 years
Interest Rate Swaps - $200M [Member] | InterestRateSwaps [Member]
Derivative
Derivative, Inception Date	30-Mar-12
Derivative, Notional Amount	200,000,000
Interest Rate Swaps - $200M [Member] | Interest Rate Swaps
Derivative
Derivative, Maturity Date	30-Mar-17
Interest Rate Swaps - $200M (2) | Interest Rate Swaps
Derivative
Derivative, Maturity Date	1-Oct-16
Derivative, Inception Date	1-Oct-13
Derivative, Notional Amount	$200,000,000

Derivatives_and_Other_Financia3

Derivatives and Other Financial Instruments (Summary of Derivative Instruments) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Unsecured Term Loan Due 2017 GBP Portion
Derivative
Foreign Currency Exchange Rate, Translation	1.48		1.56
Interest Rate Swaps
Derivative
Derivative, Notional Amount	$548,030
Derivative, Fair Value, Net	-2,427	[1]	-1,526	[1]
Interest Rate Swaps | Interest Rate Swaps - $200M (1)
Derivative
Derivative, Fixed Interest Rate	1.16%
Derivative, Maturity Date	30-Mar-17
Derivative, Fair Value, Net	-1,960	[1]	-1,448	[1]
Interest Rate Swaps | Interest Rate Swaps - $200M (2)
Derivative
Derivative, Notional Amount	200,000
Derivative, Fixed Interest Rate	0.70%
Derivative, Effective Date	1-Oct-13
Derivative, Maturity Date	1-Oct-16
Derivative, Fair Value, Net	-569	[1]	-186	[1]
Interest Rate Swaps | Interest Rate Swap - 50M GBP (1)
Derivative
Derivative, Notional Amount	74,015	[2]
Derivative, Fixed Interest Rate	0.73%	[2]
Derivative, Effective Date	2-Aug-12	[2]
Derivative, Maturity Date	30-Mar-17	[2]
Derivative, Fair Value, Net	59	[1],[2]	63	[1],[2]
Interest Rate Swaps | Interest Rate Swap - 50M GBP (2)
Derivative
Derivative, Notional Amount	74,015	[2]
Derivative, Fixed Interest Rate	0.74%	[2]
Derivative, Effective Date	2-Aug-12	[2]
Derivative, Maturity Date	30-Mar-17	[2]
Derivative, Fair Value, Net	$43	[1],[2]	$45	[1],[2]
[1]	Fair-value of derivative instruments does not include any related accrued interest payable, which is included in accrued expenses on the accompanying consolidated balance sheets. Derivative valuations are classified in Level 2 of the fair-value hierarchy. Assets are included in other assets and liabilities are included in accounts payable, accrued expenses and other liabilities on the accompanying consolidated balance sheets.
[2]	Translation to U.S. dollars is based on exchange rates of $1.48 to £1.00 and $1.56 to £1.00 at MarchB 31, 2015 and DecemberB 31, 2014, respectively.

Derivatives_and_Other_Financia4

Derivatives and Other Financial Instruments (Summary of Derivative Instruments, Effect on OCI) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	($2,502)
Derivative Instruments, Loss Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing	-170
Derivative Instruments, Gain Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing		162
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		2,550
Derivative, Gain (Loss) on Derivative, Net	-170	162
Interest Rate Swaps
Derivative
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	-839
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		859
Forward Starting Swaps
Derivative
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	-1,663
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		1,691
Parent Company
Derivative
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	-32,235
Parent Company | Interest Rate Swaps
Derivative
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax		-1,449
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Parent Company | Interest Rate Swaps
Derivative
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	$2,202

FairValue_of_Financial_Instrum2

Fair-Value of Financial Instruments (Fair-Value and Carrying Value of the Company's Financial Instruments) (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Fair-Value of Financial Instruments
Available-for-sale securities	$85,971	[1]	$58,621	[1]
Unsecured Term Loan Due 2017 GBP Portion
Fair-Value of Financial Instruments
Foreign Currency Exchange Rate, Translation	1.48		1.56
Mortgage Notes Payable
Fair-Value of Financial Instruments
Mortgage notes payable, net	503,200		496,757
Exchangeable Senior Notes
Fair-Value of Financial Instruments
Exchangeable senior notes			95,678
Unsecured Senior Notes
Fair-Value of Financial Instruments
Unsecured senior notes, net	1,294,255		1,293,903
Unsecured Line of Credit
Fair-Value of Financial Instruments
Unsecured line of credit	226,000	[2]	84,000	[2]
Fair-Value
Fair-Value of Financial Instruments
Derivative Instruments			1,132
Available-for-sale securities	85,971	[3]	58,621	[3]
Fair-Value | Mortgage Notes Payable
Fair-Value of Financial Instruments
Mortgage notes payable, net	508,782	[3]	502,115	[3]
Fair-Value | Exchangeable Senior Notes
Fair-Value of Financial Instruments
Exchangeable senior notes			134,619	[3]
Fair-Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Sixteen [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	409,600	[3]	411,600	[3]
Fair-Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Nineteen [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	402,100	[3]	398,280	[3]
Fair-Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Twenty [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	285,250	[3]	283,250	[3]
Fair-Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Twenty-Two [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	260,000	[3]	258,250	[3]
Fair-Value | Unsecured Term Loans | Unsecured Term Loan USD Portion [Member] | USD
Fair-Value of Financial Instruments
Unsecured senior term loans	244,797	[3]	244,945	[3]
Fair-Value | Unsecured Term Loans | Unsecured Term Loan Due 2017 GBP Portion | GBP
Fair-Value of Financial Instruments
Unsecured senior term loans	148,758	[3],[4]	156,589	[3],[4]
Fair-Value | Unsecured Term Loans | Unsecured Term Loan Due 2018 [Member]
Fair-Value of Financial Instruments
Unsecured senior term loans	350,515	[3]	350,557	[3]
Fair-Value | Unsecured Line of Credit
Fair-Value of Financial Instruments
Unsecured line of credit	225,668	[3]	83,866	[3]
Carrying Value
Fair-Value of Financial Instruments
Derivative Instruments	2,203
Available-for-sale securities	85,971		58,621
Carrying Value | Mortgage Notes Payable
Fair-Value of Financial Instruments
Mortgage notes payable, net	503,200		496,757
Carrying Value | Exchangeable Senior Notes
Fair-Value of Financial Instruments
Exchangeable senior notes			95,678
Carrying Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Sixteen [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	399,435		399,304
Carrying Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Nineteen [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	397,984		397,873
Carrying Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Twenty [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	248,512		248,450
Carrying Value | Unsecured Senior Notes | Unsecured Senior Notes Due Twenty Twenty-Two [Member]
Fair-Value of Financial Instruments
Unsecured senior notes, net	248,324		248,275
Carrying Value | Unsecured Term Loans | Unsecured Term Loan USD Portion [Member] | USD
Fair-Value of Financial Instruments
Unsecured senior term loans	243,596		243,596
Carrying Value | Unsecured Term Loans | Unsecured Term Loan Due 2017 GBP Portion | GBP
Fair-Value of Financial Instruments
Unsecured senior term loans	148,030	[4]	155,730	[4]
Carrying Value | Unsecured Term Loans | Unsecured Term Loan Due 2018 [Member]
Fair-Value of Financial Instruments
Unsecured senior term loans	350,000		350,000
Carrying Value | Unsecured Line of Credit
Fair-Value of Financial Instruments
Unsecured line of credit	$226,000		$84,000
[1]	Determination of fair-value is classified as Level 1 in the fair-value hierarchy based on the use of quoted prices in active markets.
[2]	At MarchB 31, 2015, the Operating Partnership had additional borrowing capacity under the unsecured line of credit of up to approximately $674.0 million
[3]	Fair-values of debt and derivative instruments are classified in Level 2 of the fair-value hierarchy. Fair-value of available-for-sale securities are classified in Level 1 of the fair-value hierarchy.
[4]	The principal balance represents the U.S. dollar amount based on the exchange rate of $1.48 to £1.00 and $1.56 to £1.00 at MarchB 31, 2015 and DecemberB 31, 2014, respectively.

Acquisitions_Narrative_Details

Acquisitions (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015
Business Acquisition
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	2.50%
307 Westlake [Member] [Member]
Business Acquisition
Business Acquisition, Description of Acquired Entity	307 Westlake
Real Estate Investments, Net	$85,733,000
Payments to Acquire Businesses, Gross	89,700,000
Business Acquisition, Effective Date of Acquisition	11-Feb-15
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	1,000,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual	200,000
Leases, Acquired-in-Place, Market Adjustment [Member]
Business Acquisition
Finite-Lived Intangible Asset, Useful Life	96 months
Leases, Acquired-in-Place, Market Adjustment [Member] | 307 Westlake [Member] [Member]
Business Acquisition
Finite-lived Intangible Assets Acquired	-1,824,000
Leases, Acquired-in-Place [Member]
Business Acquisition
Finite-Lived Intangible Asset, Useful Life	95 months
Leases, Acquired-in-Place [Member] | 307 Westlake [Member] [Member]
Business Acquisition
Finite-lived Intangible Assets Acquired	$5,791,000

Uncategorized_Items

Uncategorized Items
[us-gaap_DebtInstrumentUnamortizedPremium]	3,966,000	3,966,000