Summary of Significant Accounting Policies (Geographic Concentration) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) asset_type	Dec. 31, 2014	Dec. 31, 2013
Concentration Risk [Line Items]
Mineral rights | $	$ 0.1
Concentration Risk, Percentage	100.00%	100.00%	100.00%
Number of asset types | asset_type	3
Geographic Concentration Risk [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	10.00%
Geographic Concentration Risk [Member] | Sales [Member] | Missouri
Concentration Risk [Line Items]
Concentration Risk, Percentage	60.00%
Geographic Concentration Risk [Member] | Sales [Member] | Texas
Concentration Risk [Line Items]
Concentration Risk, Percentage	32.00%
Geographic Concentration Risk [Member] | Sales [Member] | Colorado
Concentration Risk [Line Items]
Concentration Risk, Percentage	8.00%
Asset type | Sales [Member] | Hotel
Concentration Risk [Line Items]
Concentration Risk, Percentage	68.00%
Asset type | Sales [Member] | Office Building [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	28.00%
Asset type | Sales [Member] | Multifamily [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	4.00%