Litigation, Claims, Contingencies and Other (Details Textual) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011 Rate	Dec. 31, 2012	Dec. 31, 2005
Loss Contingencies [Line Items]
Environment remediation liability included in other current liabilities	$ 643,000	$ 755,000
Environment remediation liability included in other deferred items and liabilities	4,769,000	4,999,000
Litigation Claims Contingencies and Other (Textual) [Abstract]
Environmental remediation liability	5,400,000
Maximum potential amount of future payments	24,800,000
Concession Contact expiration date range start				Dec. 31, 2005
Concession contract expiration date range end			Dec. 31, 2012
Original new contract possible term	25 years
Extended period of concession contract	7 years
Segment operating income		19.00%
New contract possible term 1	10 years
New contract possible term 2	15 years
New contract possible term 3	20 years
Revenue through concession contract		45.00%
Operating lease term	42 years
Guarantees relate to leased facilities expiry date	October 2017
Recourse provision to recover guarantees	0
Ground lease end date	Jan. 31, 2052
Other current liabilities [Member]
Loss Contingencies [Line Items]
Environment remediation liability included in other current liabilities	643,000
Other deferred items and liabilities [Member]
Loss Contingencies [Line Items]
Environment remediation liability included in other deferred items and liabilities	$ 4,800,000