Acquisitions, Dispositions and Mortgage Repayments (Details 2) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2012		Mar. 31, 2011	Mar. 31, 2010	Dec. 31, 2012 sqft		Dec. 31, 2011 sqft	Dec. 31, 2010
Real Estate Dispositions [Line Items]
Sales Price					$ 91,500,000		$ 22,800,000
Closing Adjustments					(5,500,000)		(500,000)
Mortgage Notes							(2,700,000)
Net Proceeds					74,817,000		19,572,000	34,512,000
Net Real Estate Investment							17,300,000
Other (including receivables)							1,100,000
Square Footage							181,620
Total dispositions and repayments Mortgage Note Receivable					13,500,000
Total dispositions and repayments Net Proceeds					134,600,000		36,800,000
Total dispositions and repayments Net Real Estate Investment					121,600,000
Total dispositions and repayments Other (including receivables)					(600,000)
Total dispositions and repayments Gain/Impairment					100,000		5,300,000
Total dispositions and repayments Square Footage					871,428
Mortgage Interest					9,186,000		6,973,000	2,377,000
General and administrative	400,000		200,000	200,000	20,908,000		20,990,000	16,886,000
Florida [Member] | Medical Office Buildings Disposed February 2011 [Member]
Real Estate Dispositions [Line Items]
Gain/ (Impairment)							0
Real estate dispositions [Member]
Real Estate Dispositions [Line Items]
Sales Price					91,500,000		22,800,000
Closing Adjustments					(5,500,000)		(500,000)
Mortgage Notes					(11,200,000)		(2,700,000)
Net Proceeds					74,800,000		19,600,000
Net Real Estate Investment					83,400,000		17,300,000
Other (including receivables)					2,800,000		1,100,000
Gain/ (Impairment)					(200,000)		3,900,000
Square Footage					757,826		181,620
Real estate dispositions [Member] | Medical Office Buidlings Disposed January 2012 [Member]
Real Estate Dispositions [Line Items]
Number of properties sold					2
Real estate dispositions [Member] | Texas [Member] | Medical Office Buidlings Disposed January 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Jan. 10, 2012	[1],[2],[3]
Sales Price					3,500,000	[1],[2],[3]
Closing Adjustments					(100,000)	[1],[2],[3]
Mortgage Notes					(3,000,000)	[1],[2],[3]
Net Proceeds					400,000	[1],[2],[3]
Net Real Estate Investment					2,500,000	[1],[2],[3]
Other (including receivables)					0	[1],[2],[3]
Gain/ (Impairment)					900,000	[1],[2],[3]
Square Footage					33,726	[1],[2],[3]
Number of properties sold					2
Real estate dispositions [Member] | Texas [Member] | Medical Office Buildings Disposed March 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Mar. 16, 2012	[1],[4]
Sales Price					4,700,000	[1],[4]
Closing Adjustments					(200,000)	[1],[4]
Mortgage Notes					(4,500,000)	[1],[4]
Net Proceeds					0	[1],[4]
Net Real Estate Investment					4,800,000	[1],[4]
Other (including receivables)					100,000	[1],[4]
Gain/ (Impairment)					(400,000)	[1],[4]
Square Footage					82,664	[1],[4]
Real estate dispositions [Member] | Texas [Member] | Medical Office Buildings Disposed July 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Jul. 20, 2012	[1]
Sales Price					600,000	[1]
Closing Adjustments					(100,000)	[1]
Mortgage Notes					0	[1]
Net Proceeds					500,000	[1]
Net Real Estate Investment					500,000	[1]
Other (including receivables)					0	[1]
Gain/ (Impairment)					0	[1]
Square Footage					16,578	[1]
Real estate dispositions [Member] | Texas [Member] | Medical Office Buildings Disposed August 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Aug. 27, 2012
Sales Price					21,400,000
Closing Adjustments					(2,400,000)
Mortgage Notes					0
Net Proceeds					19,000,000
Net Real Estate Investment					12,000,000
Other (including receivables)					700,000
Gain/ (Impairment)					6,300,000
Square Footage					80,740
Real estate dispositions [Member] | Florida [Member] | Medical Office Buidlings Disposed January 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Jan. 19, 2012	[1]
Sales Price					7,200,000	[1]
Closing Adjustments					(1,500,000)	[1]
Mortgage Notes					0	[1]
Net Proceeds					5,700,000	[1]
Net Real Estate Investment					3,000,000	[1]
Other (including receivables)					200,000	[1]
Gain/ (Impairment)					2,500,000	[1]
Square Footage					35,752	[1]
Real estate dispositions [Member] | Florida [Member] | Medical Office Buildings Disposed March 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Mar. 02, 2012	[1]
Sales Price					500,000	[1]
Closing Adjustments					0	[1]
Mortgage Notes					0	[1]
Net Proceeds					500,000	[1]
Net Real Estate Investment					500,000	[1]
Other (including receivables)					0	[1]
Gain/ (Impairment)					0	[1]
Square Footage					33,895	[1]
Real estate dispositions [Member] | Florida [Member] | Medical Office Buidlings Disposed April 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Apr. 18, 2012	[5]
Sales Price					33,300,000	[5]
Closing Adjustments					(900,000)	[5]
Mortgage Notes					(3,700,000)	[5]
Net Proceeds					28,700,000	[5]
Net Real Estate Investment					31,200,000	[5]
Other (including receivables)					1,300,000	[5]
Gain/ (Impairment)					(100,000)	[5]
Square Footage					272,571	[5]
Number of properties included					5
Real estate dispositions [Member] | Florida [Member] | Medical Office Buildings Disposed August 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Aug. 22, 2012	[1]
Sales Price					500,000	[1]
Closing Adjustments					0	[1]
Mortgage Notes					0	[1]
Net Proceeds					500,000	[1]
Net Real Estate Investment					900,000	[1]
Other (including receivables)					0	[1]
Gain/ (Impairment)					(400,000)	[1]
Square Footage					8,990	[1]
Real estate dispositions [Member] | Florida [Member] | Medical Office Buildings Disposed September 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Sep. 14, 2012	[2]
Sales Price					8,800,000	[2]
Closing Adjustments					(100,000)	[2]
Mortgage Notes					0	[2]
Net Proceeds					8,700,000	[2]
Net Real Estate Investment					10,800,000	[2]
Other (including receivables)					400,000	[2]
Gain/ (Impairment)					(2,500,000)	[2]
Square Footage					71,345	[2]
Real estate dispositions [Member] | Florida [Member] | Medical Office Buildings Disposed December 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Dec. 17, 2012
Sales Price					2,100,000
Closing Adjustments					(100,000)
Mortgage Notes					0
Net Proceeds					2,000,000
Net Real Estate Investment					9,700,000
Other (including receivables)					0
Gain/ (Impairment)					(7,700,000)
Square Footage					62,271
Real estate dispositions [Member] | Florida [Member] | Medical Office Buildings Disposed February 2011 [Member]
Real Estate Dispositions [Line Items]
Date Disposed							Feb. 03, 2011
Sales Price							3,200,000
Closing Adjustments							(100,000)
Mortgage Notes							(2,700,000)
Net Proceeds							400,000
Net Real Estate Investment							3,100,000
Other (including receivables)							0
Square Footage							28,861
Real estate dispositions [Member] | Florida [Member] | Medical Office Buildings Disposed August 2011 [Member]
Real Estate Dispositions [Line Items]
Date Disposed							Aug. 09, 2011
Sales Price							1,300,000
Closing Adjustments							(100,000)
Mortgage Notes							0
Net Proceeds							1,200,000
Net Real Estate Investment							2,800,000
Other (including receivables)							0
Gain/ (Impairment)							(1,600,000)
Square Footage							16,256
Real estate dispositions [Member] | Tennessee [Member] | Medical Office Buidlings Disposed April 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Apr. 13, 2012	[1]
Sales Price					900,000	[1]
Closing Adjustments					(100,000)	[1]
Mortgage Notes					0	[1]
Net Proceeds					800,000	[1]
Net Real Estate Investment					800,000	[1]
Other (including receivables)					0	[1]
Gain/ (Impairment)					0	[1]
Square Footage					18,476	[1]
Real estate dispositions [Member] | Iowa [Member] | Medical Office Buildings Disposed December 2012 [Member]
Real Estate Dispositions [Line Items]
Date Disposed					Dec. 12, 2012	[2]
Sales Price					8,000,000	[2]
Closing Adjustments					0	[2]
Mortgage Notes					0	[2]
Net Proceeds					8,000,000	[2]
Net Real Estate Investment					6,700,000	[2]
Other (including receivables)					100,000	[2]
Gain/ (Impairment)					1,200,000	[2]
Square Footage					40,818	[2]
Number of properties sold					2
Real estate dispositions [Member] | Maryland [Member] | Medical Office Buildings Disposed January 2011 [Member]
Real Estate Dispositions [Line Items]
Date Disposed							Jan. 19, 2011
Sales Price							3,700,000
Closing Adjustments							(300,000)
Mortgage Notes							0
Net Proceeds							3,400,000
Net Real Estate Investment							3,500,000
Other (including receivables)							0
Gain/ (Impairment)							(100,000)
Square Footage							35,761
Real estate dispositions [Member] | Massachusetts [Member] | Medical Office Buildings Disposed December 2011 [Member]
Real Estate Dispositions [Line Items]
Date Disposed							Dec. 12, 2011
Sales Price							3,200,000
Closing Adjustments							0
Mortgage Notes							0
Net Proceeds							3,200,000
Net Real Estate Investment							1,600,000
Other (including receivables)							0
Gain/ (Impairment)							1,600,000
Square Footage							24,900
Real estate dispositions [Member] | Massachusetts One [Member] | Medical Office Buildings Disposed December 2011 [Member]
Real Estate Dispositions [Line Items]
Date Disposed							Dec. 12, 2011
Sales Price							11,400,000
Closing Adjustments							0
Mortgage Notes							0
Net Proceeds							11,400,000
Net Real Estate Investment							6,300,000
Other (including receivables)							1,100,000
Gain/ (Impairment)							4,000,000
Square Footage							75,842
Mortgage note repayments [Member]
Real Estate Dispositions [Line Items]
Mortgage Notes					24,700,000
Net Proceeds					24,700,000		17,200,000
Gain/ (Impairment)							1,400,000
Deconsolidation of Vie [Member]
Real Estate Dispositions [Line Items]
Net Proceeds					35,100,000	[6]
Net Real Estate Investment					38,200,000	[6]
Other (including receivables)					(3,400,000)	[6]
Gain/ (Impairment)	300,000	[6]			300,000	[6]
Total dispositions and repayments Square Footage					113,602	[6]
Mortgage Interest	400,000				400,000
General and administrative	$ 100,000				$ 100,000

[1] Previously included in assets held for sale.

[2] Includes two properties.

[3] Mortgage note was repaid in November 2012.

[4] Mortgage note was repaid in April 2012.

[5] Includes five properties.

[6] “Other” includes construction liabilities transferred upon deconsolidation. “Gain” includes $0.4 million of net mortgage interest income recognized, partially offset by $0.1 million of general and administrative overhead expense that had been capitalized into the project that was reversed upon deconsolidation.