Acquisitions, Dispositions and Mortgage Repayments - Additional information (Details) (USD $)	12 Months Ended				1 Months Ended	3 Months Ended			0 Months Ended	1 Months Ended
	Dec. 31, 2014 sqft		Dec. 31, 2013 sqft		Apr. 30, 2014	Jun. 30, 2014	Dec. 31, 2014 sqft		Jan. 10, 2014	Jan. 31, 2015 building	Dec. 31, 2012 sqft	Mar. 31, 2014
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Seller Financed Mortgage Notes Receivable	$ (3,000,000)		$ 3,700,000				$ (3,000,000)
Area Covered Under Real Estate Investment Sold in Measurement Units	476,536		541,502				476,536
Elimination of Construction Mortgage Note Receivable	81,200,000		97,200,000
Total real estate properties	3,258,279,000		3,067,187,000				3,258,279,000
Noncontrolling interests	0		1,809,000				0
Real Estate Investment Net Disposed of During Period	28,200,000		76,700,000				28,200,000
Disposition Sales Price	34,900,000		101,900,000				34,900,000
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	5,500,000		21,400,000
Proceeds from sale of cost method investment in real estate	37,200,000		96,700,000
Closing Adjustments Disposed Entity	700,000		1,500,000				700,000
Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Seller Financed Mortgage Notes Receivable	1,900,000		4,300,000				1,900,000
Area Covered Under Real Estate Investment Sold in Measurement Units	476,536		541,502				476,536
Real Estate Investment Net Disposed of During Period	28,200,000		76,700,000				28,200,000
Disposition Sales Price	34,900,000		101,900,000				34,900,000
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	5,500,000		21,400,000
Proceeds from sale of cost method investment in real estate	32,300,000		96,100,000
Closing Adjustments Disposed Entity	700,000		1,500,000				700,000
Mortgage note repayments [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Seller Financed Mortgage Notes Receivable	(4,900,000)		(600,000)				(4,900,000)
Proceeds from sale of cost method investment in real estate	4,900,000		600,000
Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	673,454		940,925				673,454
Purchase Price	168,500,000		315,200,000
Payments to Acquire Businesses, Gross	69,100,000	[1]	178,400,000	[1]
Business Combination, Consideration Transferred, Liabilities Incurred	18,200,000	[2]	39,600,000	[2]
Elimination of Construction Mortgage Note Receivable			97,200,000
Notes Assumed, Unamortized Premium	1,400,000		1,400,000
Iowa [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	152,655						152,655
Purchase Price	0
Oklahoma One [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	200,000						200,000
Face Amount	81,200,000						81,200,000
Purchase Price	85,400,000
Percentage of Medical Office Building Leased	100.00%						100.00%
Payments to Acquire Businesses, Gross	4,200,000
Elimination of Construction Mortgage Note Receivable	5,000,000
Anticipated Amount of Investment	800,000						800,000
Total real estate properties	91,200,000						91,200,000
Tennessee [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Percentage of Medical Office Building Leased			100.00%
Tennessee [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			52,225								39,345
Purchase Price			16,200,000
Number of Tenants Occupying Building			4
Payments to Acquire Businesses, Gross			16,200,000	[1]
Florida [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units			14,322
Real Estate Investment Net Disposed of During Period			800,000
Impairment of Real Estate			100,000
Florida [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	47,962						47,962
Purchase Price	7,900,000
Percentage of Medical Office Building Leased	89.00%						89.00%
Payments to Acquire Businesses, Gross	7,900,000	[1]
Texas [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Contractual interest rates	5.35%						5.35%
Capital Contribution Proceeds From Minority Shareholders	1,800,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	40.00%				40.00%		40.00%
Partnership, Ownership Percentage	60.00%						60.00%
Partnership, Permanent Mortgage Loan Upon Settlement of Equity Contributions	14,200,000						14,200,000
Partnership, Consolidated Mortgage Loan	13,700,000						13,700,000
Purchase of Noncontrolling Interests					8,200,000
Noncontrolling interests	1,600,000						1,600,000
Decrease to additional paid-in capital	(6,600,000)
Texas [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	48,048						48,048
Purchase Price	8,700,000
Payments to Acquire Businesses, Gross	8,700,000	[1]
Oklahoma Two [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	68,860						68,860
Interest Rate	6.10%
Purchase Price	17,500,000
Percentage of Medical Office Building Leased	97.00%						97.00%
Significant Acquisitions and Disposals, Acquisition Related Costs	10,700,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	6,800,000						6,800,000
Notes Assumed, Unamortized Premium	400,000
Washington [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	60,161		81,956				60,161
Contractual interest rates			6.01%
Percentage of Property Leased			100.00%
Purchase Price	22,700,000		34,900,000
Payments to Acquire Businesses, Gross	22,700,000	[1]	18,300,000	[1]
Business Combination, Consideration Transferred, Liabilities Incurred	16,600,000		16,600,000	[2]
Notes Assumed, Unamortized Premium			500,000
Percentage of Medical Office Building Occupied	98.00%						98.00%
North Carolina [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units			57,580
Real Estate Investment Net Disposed of During Period			13,400,000
North Carolina [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	35,292		90,633				35,292
Contractual interest rates			5.86%
Percentage of Property Leased			100.00%
Purchase Price	6,500,000		20,100,000
Percentage of Medical Office Building Leased	100.00%						100.00%
Payments to Acquire Businesses, Gross	6,500,000	[1]	9,100,000	[1]
Business Combination, Consideration Transferred, Liabilities Incurred			11,000,000	[2]
Notes Assumed, Unamortized Premium			200,000
Minnesota [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	60,476	[3]					60,476	[3]
Purchase Price	19,800,000	[3]
Percentage of Medical Office Building Leased	100.00%						100.00%
Payments to Acquire Businesses, Gross	8,400,000	[1],[3]
Business Combination, Consideration Transferred, Liabilities Incurred	11,400,000	[3]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	11,400,000						11,400,000
Notes Assumed, Unamortized Premium	1,000,000
Long-term Debt, Weighted Average Interest Rate	6.67%						6.67%
Indiana [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			205,573
Percentage of Property Leased			87.00%
Purchase Price			44,300,000
Payments to Acquire Businesses, Gross			44,300,000	[1]
Missouri [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			186,000
Purchase Price			102,600,000
Payments to Acquire Businesses, Gross			5,400,000	[1]
Elimination of Construction Mortgage Note Receivable			97,200,000
Missouri [Member] | Additional Funding [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Elimination of Construction Mortgage Note Receivable	2,300,000		6,500,000
Texas One [Member] | Texas [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			42,627
Percentage of Property Leased			100.00%
Purchase Price			16,300,000
Number of Tenants Occupying Building			1
Payments to Acquire Businesses, Gross			16,300,000	[1]
Texas Two [Member] | Texas [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			97,552
Percentage of Property Leased			88.00%
Purchase Price			19,000,000
Payments to Acquire Businesses, Gross			19,000,000	[1]
Colorado One [Member] | Colorado [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			80,153
Contractual interest rates			6.17%
Percentage of Property Leased			100.00%
Purchase Price			33,200,000
Payments to Acquire Businesses, Gross			21,200,000	[1]
Business Combination, Consideration Transferred, Liabilities Incurred			12,000,000	[2]
Notes Assumed, Unamortized Premium			700,000
Colorado Two [Member] | Colorado [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			70,138
Percentage of Property Leased			83.00%
Purchase Price			21,600,000
Payments to Acquire Businesses, Gross			21,600,000	[1]
Colorado Three [Member] | Colorado [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage			34,068
Percentage of Property Leased			100.00%
Purchase Price			7,000,000
Payments to Acquire Businesses, Gross			7,000,000	[1]
Medical Building Disposed May 24 2013 [Member] | Texas [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units			100,920	[4]
Real Estate Investment Net Disposed of During Period			3,000,000	[4]
Impairment of Real Estate			6,800,000
Disposition Sales Price			3,200,000	[4]
Proceeds from sale of cost method investment in real estate			3,000,000	[4]
Closing Adjustments Disposed Entity			200,000	[4]
Medical Building Disposed June 2013 [Member] | Iowa [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Real Estate Dispositions Mortgage Note Receivable			1,100,000
Medical Building Disposed June 2013 [Member] | Iowa [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units			31,725	[5],[6]
Real Estate Investment Net Disposed of During Period			5,300,000	[5],[6]
Number of properties sold			2
Disposition Sales Price			6,900,000	[5],[6]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property			1,400,000	[5],[6]
Proceeds from sale of cost method investment in real estate			6,900,000	[5],[6]
Real Estate Dispositions Mortgage Note Receivable			1,100,000
Medical Building Disposed June 2013 [Member] | Iowa Two [Member] | Iowa [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units			22,572
Medical Building Disposed June 2013 [Member] | Iowa One [Member] | Iowa [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units			9,153
Medical Building Disposed April 11 2014 [Member] | Florida [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units	52,608	[4]					52,608	[4]
Real Estate Investment Net Disposed of During Period	1,700,000	[4]					1,700,000	[4]
Impairment of Long-Lived Assets to be Disposed of	3,300,000
Disposition Sales Price	1,800,000	[4]					1,800,000	[4]
Proceeds from sale of cost method investment in real estate	1,700,000	[4]
Closing Adjustments Disposed Entity	100,000	[4]					100,000	[4]
Medical Building Disposed April 23 2014 [Member] | Texas [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units	58,365	[4]					58,365	[4]
Real Estate Investment Net Disposed of During Period	4,100,000	[4]					4,100,000	[4]
Impairment of Long-Lived Assets to be Disposed of	2,600,000
Disposition Sales Price	4,400,000	[4]					4,400,000	[4]
Proceeds from sale of cost method investment in real estate	4,200,000	[4]
Closing Adjustments Disposed Entity	200,000	[4]					200,000	[4]
Medical Building Disposed September 2014 [Member] | Nevada [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Seller Financed Mortgage Notes Receivable	1,900,000						1,900,000
Area Covered Under Real Estate Investment Sold in Measurement Units	31,026						31,026
Real Estate Investment Net Disposed of During Period	4,900,000						4,900,000
Impairment of Long-Lived Assets to be Disposed of	2,800,000
Disposition Sales Price	2,300,000						2,300,000
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	(2,800,000)
Proceeds from sale of cost method investment in real estate	200,000
Closing Adjustments Disposed Entity	200,000						200,000
Medical Building Disposed November 2014 [Member] | Tennessee [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units	32,204	[6]					32,204	[6]
Real Estate Investment Net Disposed of During Period	3,200,000	[6]					3,200,000	[6]
Impairment of Long-Lived Assets to be Disposed of	400,000
Number of Medical Office Disposed Off Campus	2						2
Disposition Sales Price	3,100,000	[6]					3,100,000	[6]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	(400,000)	[6]
Proceeds from sale of cost method investment in real estate	2,900,000	[6]
Closing Adjustments Disposed Entity	200,000	[6]					200,000	[6]
Medical Building Disposed November 2014 [Member] | Texas [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units	166,167	[6]					166,167	[6]
Real Estate Investment Net Disposed of During Period	12,100,000	[6]					12,100,000	[6]
Number of Medical Office Disposed Off Campus	2						2
Disposition Sales Price	21,500,000	[6]					21,500,000	[6]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	9,200,000	[6]
Proceeds from sale of cost method investment in real estate	21,500,000	[6]
Medical Building Disposed December 2014 [Member] | Missouri [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units	26,166	[4]					26,166	[4]
Real Estate Investment Net Disposed of During Period	1,400,000	[4]					1,400,000	[4]
Impairment of Long-Lived Assets to be Disposed of	200,000					3,100,000
Disposition Sales Price	1,300,000	[4]					1,300,000	[4]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	(200,000)	[4]
Proceeds from sale of cost method investment in real estate	1,300,000	[4]
Medical Building Disposed December 2014 [Member] | Illinois [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units	110,000	[4]					110,000	[4]
Real Estate Investment Net Disposed of During Period	800,000	[4]					800,000	[4]
Impairment of Long-Lived Assets to be Disposed of	300,000						5,600,000
Disposition Sales Price	500,000	[4]					500,000	[4]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	(300,000)	[4]
Proceeds from sale of cost method investment in real estate	500,000	[4]
Land Disposed March 2013 [Member] | Texas [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Seller Financed Mortgage Notes Receivable			3,700,000
Area Covered Under Real Estate Investment Sold in Measurement Units			15.1
Real Estate Investment Net Disposed of During Period			8,100,000
Disposition Sales Price			5,000,000
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property			(3,300,000)
Proceeds from sale of cost method investment in real estate			1,100,000
Closing Adjustments Disposed Entity			200,000
Land Disposed March 2013 [Member] | Texas [Member] | Real estate dispositions [Member] | Minimum [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Contractual interest rates			5.00%
Land Disposed March 2013 [Member] | Texas [Member] | Real estate dispositions [Member] | Maximum [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Contractual interest rates			6.00%
Building Disposed April 2013 [Member] | Tennessee [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Area Covered Under Real Estate Investment Sold in Measurement Units			17,696
Real Estate Investment Net Disposed of During Period			400,000
Impairment of Real Estate			1,300,000
Disposition Sales Price			600,000
Deferred Gain on Disposition of Assets			200,000
Building Disposed April 2013 [Member] | Tennessee [Member] | Real estate dispositions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Seller Financed Mortgage Notes Receivable			600,000	[4],[7]
Area Covered Under Real Estate Investment Sold in Measurement Units			17,696	[4],[7]
Contractual interest rates			7.50%
Real Estate Investment Net Disposed of During Period			400,000	[4],[7]
Disposition Sales Price			600,000	[4],[7]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property			200,000	[4],[7]
Other Mortgage Loans [Member] | Other Property [Member] | Iowa [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage	152,655						152,655
Face Amount	40,000,000						40,000,000					40,000,000
Interest Rate	7.70%								7.70%
Incremental Interest Rate for Default	3.00%
Percentage of Property Leased	93.00%
Medical Office Building [Member] | Texas [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Purchase Price	8,700,000
Limited Liability Company, Ownership Percentage	56.90%						56.90%
Real Estate [Member] | Medical Office Building [Member] | Texas [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Percentage of Medical Office Building Leased	95.00%						95.00%
St Josephs Medical Center [Member] | Indiana [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Percentage of Property Leased			48.00%
Poudre Valley Health System [Member] | Colorado One [Member] | Colorado [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Percentage of Property Leased			71.00%
Mercy Health [Member] | Missouri [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Percentage of Property Leased			100.00%
Seton Healthcare [Member] | Texas Two [Member] | Texas [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Percentage of Property Leased			24.00%
Subsequent Event [Member] | California [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Percentage of Property Leased										97.00%
Purchase Price										$ 39,300,000
Number of Medical Office Buildings in Health System										2
Subsequent Event [Member] | Kaiser Permanente and Washington Hospital Healthcare System [Member] | California [Member] | Real estate acquisitions [Member]
Real Estate Acquisitions and Mortgage Note Financing [Line Items]
Business Acquisition Purchase Price Allocation Square Footage										110,679
Percentage of Property Leased										59.00%

[1] Cash consideration excludes non-real estate assets acquired and liabilities assumed in the acquisitions.

[2] The mortgage notes payable assumed in the acquisitions do not reflect the fair value adjustments totaling $1.4 million recorded by the Company upon acquisition (included in Other).

[3] The mortgage notes payable assumed in the acquisitions do not reflect the fair value adjustment totaling $1.4 million recorded by the Company upon acquisition (included in Other).

[4] Previously included in assets held for sale.

[5] The Company repaid a mortgage note payable of $1.1 million upon sale and incurred debt extinguishment costs of $0.3 million.

[6] Includes two properties.

[7] The Company-financed mortgage note receivable was repaid in October 2013.