Commitments and Contingencies - Construction Activity (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($) a ft² property	Sep. 30, 2015 USD ($) a ft² property	Dec. 31, 2014 USD ($)	Dec. 31, 2006 USD ($)
Other Commitments [Line Items]
Number of Properties | property	195	195
Land held for redevelopment	$ 17,475	$ 17,475	$ 17,054
Approximate Square Feet | ft²	14,100,000	14,100,000
ALABAMA
Other Commitments [Line Items]
Total Amount Funded	$ 6,100	$ 6,100
Estimated Total Investment	$ 15,400	$ 15,400
TENNESSEE
Other Commitments [Line Items]
Number of Properties | property	2	2
Number of redevelopment properties under expansion | property	1	1
Land held for redevelopment	$ 5,000	$ 5,000
Total Amount Funded	15,000	15,000
Estimated Total Investment	$ 51,800	$ 51,800
Retail Site [Member] | TEXAS
Other Commitments [Line Items]
Number of Properties | property	1	1
Land held for redevelopment				$ 1,500
Construction in Progress Fundings During the Six Months Ended		$ 1,764
Total Funding During the Six Months Ended		1,764
Total Amount Funded	$ 1,764	1,764
Estimated Remaining Fundings	3,811	3,811
Estimated Total Investment	$ 5,575	$ 5,575
Approximate Square Feet | ft²	12,900	12,900
Medical Office Building [Member] | ALABAMA
Other Commitments [Line Items]
Number of Properties | property	1	1
Construction in Progress Fundings During the Six Months Ended		$ 4,721
Total Funding During the Six Months Ended		6,119
Total Amount Funded	$ 6,119	6,119
Estimated Remaining Fundings	9,281	9,281
Estimated Total Investment	$ 15,400	$ 15,400
Approximate Square Feet | ft²	138,000	138,000
Medical Office Building [Member] | TENNESSEE
Other Commitments [Line Items]
Number of Properties | property	2,000	2,000
Construction in Progress Fundings During the Six Months Ended		$ 8,970
Total Funding During the Six Months Ended		10,575
Total Amount Funded	$ 14,959	14,959
Estimated Remaining Fundings	36,841	36,841
Estimated Total Investment	$ 51,800	$ 51,800
Approximate Square Feet | ft²	294,000	294,000
Medical Office Buildings and Retail Sites [Member]
Other Commitments [Line Items]
Construction in Progress Fundings During the Six Months Ended		$ 15,455
Total Funding During the Six Months Ended		18,458
Total Amount Funded	$ 22,842	22,842
Estimated Remaining Fundings	49,933	49,933
Estimated Total Investment	$ 72,775	$ 72,775
Approximate Square Feet | ft²	444,900	444,900
Land Held for Development [Member] | TENNESSEE
Other Commitments [Line Items]
Area of Land | a	0.38	0.38
Payment to acquire property	$ 2,000
Land Held for Development [Member] | Medical Office Building [Member] | TENNESSEE
Other Commitments [Line Items]
Approximate Square Feet | ft²	7,672	7,672