v2.4.0.6
Accounting Policies (Details 3) (USD $)
In Thousands, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2011
property
Dec. 31, 2010
property
Dec. 31, 2009
Redeemable Limited Partnership Unitholder Interests      
Number of entity shares issued in exchange for redemption of OP Units 0.7866    
Fair value of operating partnership units exceeding cost $ 102,837 $ 0  
Noncontrolling Interest      
Number of properties having controlling interests owned through joint ventures 29 6  
Noncontrolling interest share in properties owned through joint ventures 80,987 3,479  
Net (loss) income attributable to noncontrolling interest, net of tax $ (1,232) $ 3,562 $ 2,865
NHP/PMB L.P.
     
Redeemable Limited Partnership Unitholder Interests      
Number of entity shares issued in exchange for redemption of OP Units 0.7866    
NHP/PMB L.P. | Class A Units
     
Redeemable Limited Partnership Unitholder Interests      
Limited partnership units held by third party investors (in shares) 2,371,415    
Percentage of ownership interest on total units outstanding 28.90%    
NHP/PMB L.P. | Class B Units
     
Redeemable Limited Partnership Unitholder Interests      
Percentage of ownership interest on total units outstanding 71.10%    
Limited partnership units outstanding (in shares) 5,845,038