Quarterly report pursuant to Section 13 or 15(d)

Unsecured Lines of Credit Payable - Narrative (Details)

v3.2.0.727
Unsecured Lines of Credit Payable - Narrative (Details) - USD ($)
6 Months Ended
Jun. 23, 2015
Jun. 30, 2015
Line of Credit    
Line of Credit Facility [Line Items]    
Line of Credit Facility, Commitment Fee Percentage   0.20%
Line of Credit Facility, Interest Rate During Period   1.00%
Prior Credit Facility No. 1 | Line of Credit    
Line of Credit Facility [Line Items]    
Committed capacity $ 100,000,000  
Prior Credit Facility No. 2 | Line of Credit    
Line of Credit Facility [Line Items]    
Committed capacity 400,000,000  
New Credit Facility    
Line of Credit Facility [Line Items]    
Committed capacity 1,000,000,000.0  
New Credit Facility | Line of Credit    
Line of Credit Facility [Line Items]    
Committed capacity $ 600,000,000 $ 600,000,000
Minimum [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Line of Credit Facility, Commitment Fee Percentage 0.125%  
Maximum [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Line of Credit Facility, Commitment Fee Percentage 0.30%  
London Interbank Offered Rate (LIBOR) [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Debt Instrument, Basis Spread on Variable Rate 1.00%  
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Debt Instrument, Basis Spread on Variable Rate 0.875%  
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Debt Instrument, Basis Spread on Variable Rate 1.55%  
Base Rate [Member] | Minimum [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Debt Instrument, Basis Spread on Variable Rate 0.00%  
Base Rate [Member] | Maximum [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Debt Instrument, Basis Spread on Variable Rate 0.55%  
Federal Funds Effective Swap Rate [Member] | Line of Credit    
Line of Credit Facility [Line Items]    
Debt Instrument, Basis Spread on Variable Rate 0.50%