Real Estate Investments - Narrative (Details) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended			1 Months Ended		3 Months Ended	0 Months Ended	3 Months Ended	0 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	1 Months Ended		1 Months Ended			1 Months Ended
	Jun. 30, 2014 Property	Jun. 30, 2013	Jun. 30, 2014 Property	Jun. 30, 2013	Dec. 31, 2013 Property	Jun. 30, 2014 Discontinued Operations [Member]	Jun. 30, 2013 Discontinued Operations [Member]	Jun. 30, 2014 Discontinued Operations [Member]	Jun. 30, 2013 Discontinued Operations [Member]	Dec. 31, 2013 Discontinued Operations [Member]	Apr. 30, 2014 TEXAS	Jun. 30, 2014 TEXAS	Mar. 31, 2014 Other Mortgage Loans [Member] Other Property [Member] IOWA	Apr. 23, 2014 Real Estate Dispositions [Member] TEXAS Medical Building Disposed April 2014 [Member]	Mar. 31, 2014 Real Estate Dispositions [Member] TEXAS Medical Building Disposed April 2014 [Member]	Apr. 11, 2014 Real Estate Dispositions [Member] FLORIDA Medical Building Disposed April 2014 [Member]	Mar. 31, 2014 Real Estate Dispositions [Member] FLORIDA Medical Building Disposed April 2014 [Member]	Dec. 31, 2013 Real Estate Dispositions [Member] FLORIDA Medical Building Disposed April 2014 [Member]	Jun. 30, 2014 Transferred to Held For Sale [Member] Discontinued Operations [Member]	May 31, 2014 Real Estate Acquisitions [Member] OKLAHOMA sqft	Jun. 30, 2014 Real Estate Acquisitions [Member] OKLAHOMA	Jun. 30, 2014 Real Estate Acquisitions [Member] NORTH CAROLINA sqft	Jul. 30, 2014 Real Estate Acquisitions [Member] Subsequent Event [Member] MINNESOTA sqft	Jun. 30, 2014 Medical Office Building [Member] TEXAS	Jun. 30, 2014 Real Estate Assets [Member] Medical Office Building [Member] TEXAS
Acquisitions and Dispositions [Line Items]
Square footage																				200,000		35,292	60,476
Purchase price																				$ 85,400,000		$ 6,500,000	$ 19,900,000
Percentage of medical office building leased																				100.00%		100.00%	100.00%
Face amount of mortgages													40,000,000							81,200,000
Cash consideration																				4,200,000			8,500,000
Additional funded amount																				1,700,000
Anticipated amount of investment																					4,100,000
Real estate properties, cost	3,224,561,000		3,224,561,000		3,067,187,000	15,143,000		15,143,000		16,978,000									4,300,000		91,200,000
Limited liability company, ownership percentage																								56.90%
Cash consideration																									8,800,000
Closing costs																									100,000
Stated interest rate, percent													7.70%
Incremental Interest Rate for Default													3.00%
Exit fee													1,500,000
Assumption of debt																							11,400,000
Interest rate, assumed debt, percentage																							6.67%
Real estate investment disposed of during period														4,100,000		1,700,000
Impairment charges															2,600,000		900,000	2,400,000
Disposition sales price														4,400,000		1,800,000
Net cash proceeds														4,200,000		1,700,000
Closing costs on disposition														200,000		100,000
Noncontrolling interest, ownership percentage by parent											40.00%
Purchase of noncontrolling interests											8,200,000
Noncontrolling interests	0		0		1,809,000							1,600,000
Number of Properties Reclassified to Held For Sale	1
Total real estate properties, net	2,548,671,000		2,548,671,000		2,435,078,000	5,637,000		5,637,000		6,767,000									1,400,000
Impairments	$ 3,105,000	$ 0	$ 6,529,000	$ 3,630,000		$ 3,105,000	$ 0	$ 6,529,000	$ 3,630,000										$ 3,100,000
Number of Properties Held for Sale	3		3		3