Consolidated Statement of Changes in Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Common stock/unit per share	$ 1.85	$ 1.85	$ 1.85
Parent Company [Member]
Common stock/unit per share	$ 1.85	$ 1.85	$ 1.85