Finance Receivables (Narratives) (Details) (USD $)	9 Months Ended			1 Months Ended			1 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010 China Alliance Properties Limited	Sep. 30, 2012 China Alliance Properties Limited	Dec. 31, 2011 China Alliance Properties Limited	Sep. 30, 2013 BPS Partners, LLC	Jun. 30, 2012 BPS Partners, LLC	Sep. 30, 2012 BPS Partners, LLC	Dec. 31, 2011 BPS Partners, LLC	Sep. 30, 2011 Flanders Corporation	Sep. 30, 2011 Spear Precision Packaging
Acquisitions Of Net Investments In Direct Financing Leases [Line Items]
Notes, Loans and Financing Receivable, Gross				$ 40,000,000				$ 30,000,000
Stated Interest Rates For Notes Receivable				11.00%			7.50%	0.50%
Notes Receivable	70,000,000		70,000,000		40,000,000	40,000,000			30,000,000	30,000,000
Notes Receivable Maturity Date					2015-12-01				2013-09-01
Capital Leases, Net Investment in Direct Financing Leases, Minimum Payments to be Received	4,000,000		2,000,000
Net investments in direct financing leases	474,277,000		462,505,000								50,800,000	8,000,000
DFL Acquisition fees		$ 2,600,000
Financing Receivable, Credit Quality, Additional Information	We generally seek investments in facilities that we believe are critical to each tenant’s business and that we believe have a low risk of tenant defaults. At September 30, 2012 and December 31, 2011, none of the balances of our finance receivables were past due and we had not established any allowances for credit losses. Additionally, there have been no modifications of finance receivables during the nine months ended September 30, 2012. We evaluate the credit quality of our tenant receivables utilizing an internal 5-point credit rating scale, with 1 representing the highest credit quality and 5 representing the lowest.
Financing Receivable, Credit Quality, Date Ratings Updated	Jul. 01, 2012