Annual report pursuant to Section 13 and 15(d)

Unsecured Lines Of Credit Payable - Lines Of Credit Unused and Available (Details)

v2.4.0.8
Unsecured Lines Of Credit Payable - Lines Of Credit Unused and Available (Details) (USD $)
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Line of Credit Facility [Line Items]      
Committed capacity $ 500,000,000 $ 500,000,000 $ 475,000,000
Borrowings outstanding 0 0 99,000,000
Credit Facility No. 1 [Member]
     
Line of Credit Facility [Line Items]      
Committed capacity 100,000,000    
Borrowings outstanding 0 0  
Letters of credit issued 0    
Unused and available 100,000,000    
Credit Facility No. 2 [Member]
     
Line of Credit Facility [Line Items]      
Committed capacity 400,000,000    
Borrowings outstanding 0 0  
Letters of credit issued 0    
Unused and available $ 400,000,000