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Commitments And Contingencies (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Commitments And Contingencies [Abstract]      
Lease obligations, latest maturity date 2021    
Lease rental expense $ 67 $ 48 $ 47
Number of lawsuits filed by cities, counties and states involving hotel occupancy taxes 79    
Number of lawsuits dismissed to date 25    
Number of dismissals based on finding that defendant was not subject to local hotel occupancy tax or the local government lacked standing to pursue claims 13    
Reserve for potential settlement of issues related to hotel occupancy taxes 32 24  
Accrual related to court decisions and final settlements related to hotel occupancy taxes 10 13  
Occupancy tax assessments including interest and penalties   3 48
Proceeds from exchange for a letter of credit 3    
Increase in remaining settlement liability related to class action lawsuit 2 3  
Estimated settlement cost     $ 19