Investments In Direct Financing Lease (Narrative) (Details) (USD $)	12 Months Ended	3 Months Ended
	Dec. 31, 2011	Mar. 31, 2012 Minimum [Member]	Mar. 31, 2012 Maximum [Member]	Mar. 31, 2012 Imagine Schools [Member] properties
Number of public charter school properties (in properties)				27
Allowance for lease losses	$ 0
Direct financing expiration date (in years)		20	23