Gain on Sales of Properties (Details) (New properties and properties under development, USD $)	3 Months Ended
	Mar. 31, 2014 item	Mar. 31, 2013 item
Sales of investment properties
Number of properties sold	11	17
Sales proceeds	$ 12,700,000	$ 60,000,000
Gain on sales of investment properties	3,900,000	38,600,000
Crest
Sales of investment properties
Number of properties sold	1
Sales proceeds	820,000
Gain on sales of investment properties	$ 0