XML 23 R52.htm IDEA: XBRL DOCUMENT v2.4.0.6
Debt (Narrative) (Details) (USD $)
 3 Months Ended 6 Months Ended 3 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Dec. 31, 2011
Jun. 30, 2012
Unsecured Letter Of Credit Facility [Member]
Jul. 02, 2012
Unsecured Letter Of Credit Facility [Member]
Dec. 31, 2011
Unsecured Letter Of Credit Facility [Member]
Jun. 30, 2012
Letter Of Credit [Member]
Dec. 31, 2011
Letter Of Credit [Member]
Debt Instrument                    
Extinguishment of Debt, Amount $ 0 $ 53,000,000                
Gains (Losses) on Extinguishment of Debt     0 (3,537,000)            
Maximum borrowing capacity           200,000,000 150,000,000      
Subsequent Event, Date     Jul. 02, 2012              
Credit facility expiration date           Jun. 01, 2014        
Letters of Credit Outstanding, Amount $ 200,500,000   $ 200,500,000   $ 235,900,000 $ 133,600,000   $ 152,700,000 $ 66,900,000 $ 83,200,000