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Real Estate and Accumulated Depreciation (Parenthetical) (Detail) (USD $)
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Real Estate And Accumulated Depreciation Disclosure [Abstract]      
Tax cost basis of assets $ 10,400,000,000 $ 8,700,000,000 $ 8,500,000,000
Real estate land under development 230,400,000    
Real estate construction in progress 222,600,000    
The amount of tax-exempt certificates excluded from encumbrances 15,400,000    
Fair market value of debt adjustments excluded from encumbrances $ 36,700,000