Gain on Sales of Real Estate (Details) (New properties and properties under development, USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014 item	Sep. 30, 2013 item	Sep. 30, 2014 item	Sep. 30, 2013 item
Gain on sales of real estate
Number of properties sold	11	19	28	53
Sales proceeds	$ 33,800,000	$ 22,400,000	$ 53,600,000	$ 106,100,000
Gain on sales of real estate	11,000,000	6,200,000	16,800,000	50,500,000
Crest
Gain on sales of real estate
Number of properties sold			1
Sales proceeds			820,000
Gain on sales of real estate			$ 0