Real Estate Leases and Mortgage Notes Receivable (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012 Customers		Dec. 31, 2011		Dec. 31, 2010 Customers		Dec. 31, 2009
Related Party Transaction [Line Items]
Lease fixed rent renewal term	5 years
Renewal term for lease and financial agreements	five years, or multiples thereof, in addition to market rent renewal terms
Number of customer account for 10% or more of company's revenues including revenue from discontinued operations	0				0
Mortgage notes receivable	$ 162,191,000	[1],[2]	$ 97,381,000	[1],[2]	$ 36,599,000	[1]	$ 31,008,000
Existing construction mortgage loans funded	78,300,000		19,200,000
Purchase price under purchase option provision	greater of fair market value or an amount equal to the Company’s gross investment
Approximate Investment in real estate properties subject to outstanding contractual option to purchase	206,300,000
Baylor Health System [Member]
Related Party Transaction [Line Items]
Number of customer account for 10% or more of company's revenues including revenue from discontinued operations			1
United Trust Fund [Member]
Related Party Transaction [Line Items]
Mortgage notes receivable	118,400,000
Mortgage notes receivable percentage	73.00%
Number of developing build to suit facilities	2
LB Properties X, LLC [Member]
Related Party Transaction [Line Items]
Mortgage notes receivable	$ 40,000,000
Mortgage notes receivable percentage	24.70%
Number of mortgage notes receivable outstanding	1

[1] Total mortgage notes as of December 31, 2012 had an aggregate total cost of $162.2 million for federal income tax purposes.

[2] Level 2 - Fair value based on quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-driven valuations in which significant inputs and significant value drivers are observable in active markets.