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Consolidated Statements of Equity (Parenthetical) - $ / shares
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Parent Company [Member]      
Common Stock, Dividends, Per Share, Declared $ 2.9600 $ 2.8150 $ 2.6750
Distribution Made to Limited Partner, Distributions Declared, Per Unit 2.9600 2.8150 2.6750
Limited Partner [Member]      
Distribution Made to Limited Partner, Distributions Declared, Per Unit $ 2.9600 $ 2.8150 $ 2.6750