Debt (Subsequent Events - New Unsecured Line of Credit) (Narrative) (Details) (New Unsecured Line Of Credit [Member], USD $)	6 Months Ended
Jun. 30, 2011
LOC current borrowing capacity	750,000,000
LOC maturity date	July 13, 2015
LOC maximum borrowing capacity	1,250,000,000
Reserve Adjusted LIBOR [Member] \| Maximum [Member]
Basis point spread over interest rate	0.0205%
Reserve Adjusted LIBOR [Member] \| Minimum [Member]
Basis point spread over interest rate	0.01%
Prime Rate [Member] \| Maximum [Member]
Basis point spread over interest rate	0.0125%
Prime Rate [Member] \| Minimum [Member]
Basis point spread over interest rate	0.00%
Federal Funds Rate [Member] \| Maximum [Member]
Basis point spread over interest rate	0.0175%
Federal Funds Rate [Member] \| Minimum [Member]
Basis point spread over interest rate	0.005%
One Month LIBOR [Member] \| Maximum [Member]
Basis point spread over interest rate	0.0205%
One Month LIBOR [Member] \| Minimum [Member]
Basis point spread over interest rate	0.01%
BIOMED REALTY TRUST, INC. [Member]
Company's credit rating in basis points	0.0035%

Company's Credit Rating In Basis Points

Name:	bmr_CompanySCreditRatingInBasisPoints
Namespace Prefix:	bmr
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects when the credit facility terminates, which may be presented in a variety of ways (year, month and year, day, month and year, quarter).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate
Namespace Prefix:	us-gaap
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant