Commitments and Contingencies - Construction Activity (Details) ft² in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($) ft² property	Dec. 31, 2014 USD ($)
Other Commitments [Line Items]
Land held for redevelopment	$ 16,952	$ 17,054
Number of Properties | property	196
Approximate Square Feet | ft²	14,100
TENNESSEE
Other Commitments [Line Items]
Land held for redevelopment	$ 4,300
Number of redevelopment properties under expansion | property	1
Number of Properties | property	2
Total Amount Funded	$ 12,376
Estimated Total Investment	51,800
ALABAMA
Other Commitments [Line Items]
Total Amount Funded	3,123
Estimated Total Investment	15,400
Medical Office Building [Member]
Other Commitments [Line Items]
Construction in Progress Fundings During the Six Months Ended	8,284
Total Funding During the Six Months Ended	11,115
Total Amount Funded	15,499
Estimated Remaining Fundings	51,701
Estimated Total Investment	$ 67,200
Approximate Square Feet | ft²	432,000
Medical Office Building [Member] | TENNESSEE
Other Commitments [Line Items]
Number of Properties | property	2
Construction in Progress Fundings During the Six Months Ended	$ 6,560
Total Funding During the Six Months Ended	7,992
Total Amount Funded	12,376
Estimated Remaining Fundings	39,424
Estimated Total Investment	$ 51,800
Approximate Square Feet | ft²	294,000
Medical Office Building [Member] | ALABAMA
Other Commitments [Line Items]
Number of Properties | property	1
Construction in Progress Fundings During the Six Months Ended	$ 1,724
Total Funding During the Six Months Ended	3,123
Total Amount Funded	3,123
Estimated Remaining Fundings	12,277
Estimated Total Investment	$ 15,400
Approximate Square Feet | ft²	138,000