Divestiture of Non-Core Properties (Details) (USD $)	1 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2013	Aug. 31, 2013	Sep. 30, 2012 acre	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Divestiture of Non Core Properties [Abstract]
Net proceeds from divestiture of non-core properties	$ 71,400,000		$ 21,500,000	$ 6,600,000
Proceeds from Monetization of Assets		38,300,000		10,600,000
Area of Real Estate Property			2,563
Proceeds from other property sales during the year				600,000
Gain (Loss) on Sale of Property	$ 33,400,000			$ 33,377,000	$ 0	$ 0