Quarterly report pursuant to Section 13 or 15(d)

Unsecured Lines of Credit Payable - Narrative (Details)

v3.8.0.1
Unsecured Lines of Credit Payable - Narrative (Details)
3 Months Ended
Mar. 31, 2018
USD ($)
extension_option
Mar. 29, 2018
USD ($)
Jul. 22, 2016
USD ($)
Sep. 15, 2015
USD ($)
Interest Rate Swap [Member]        
Line of Credit Facility [Line Items]        
Derivative, notional amount $ 400,000,000      
LIBOR [Member]        
Line of Credit Facility [Line Items]        
Debt instrument variable rate (percent) 1.88%      
Line of Credit        
Line of Credit Facility [Line Items]        
Commitment fee (percent) 0.20%      
Interest rate during period (percent) 1.00%      
Line of Credit | Minimum [Member]        
Line of Credit Facility [Line Items]        
Commitment fee (percent) 0.10%      
Line of Credit | Maximum [Member]        
Line of Credit Facility [Line Items]        
Commitment fee (percent) 0.30%      
Line of Credit | LIBOR [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 1.00%      
Line of Credit | LIBOR [Member] | Minimum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 0.775%      
Line of Credit | LIBOR [Member] | Maximum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 1.55%      
Line of Credit | Base Rate [Member] | Minimum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 0.00%      
Line of Credit | Base Rate [Member] | Maximum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 0.55%      
Line of Credit | Federal Funds Effective Swap Rate [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 0.50%      
2015 Term Loan [Member] | Interest Rate Swap [Member]        
Line of Credit Facility [Line Items]        
Derivative, notional amount       $ 150,000,000
Derivative, fixed interest rate (percent)       2.72%
2018 Term Loan [Member]        
Line of Credit Facility [Line Items]        
Debt instrument, face amount   $ 250,000,000    
2018 Term Loan A [Member] | Interest Rate Swap [Member]        
Line of Credit Facility [Line Items]        
Derivative, notional amount   $ 150,000,000 $ 150,000,000  
Derivative, fixed interest rate (percent)   2.31%    
2018 Term Loan A [Member] | LIBOR [Member] | Minimum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 0.85%      
2018 Term Loan A [Member] | LIBOR [Member] | Maximum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 1.75%      
2018 Term Loan A [Member] | Base Rate [Member] | Minimum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 0.00%      
2018 Term Loan A [Member] | Base Rate [Member] | Maximum [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 0.75%      
2018 Term Loan B [Member]        
Line of Credit Facility [Line Items]        
Derivative, notional amount   $ 100,000,000    
2018 Term Loan B [Member] | Interest Rate Swap [Member]        
Line of Credit Facility [Line Items]        
Derivative, notional amount   $ 100,000,000    
Derivative, fixed interest rate (percent)   3.71%    
Credit facility 2018 [Member]        
Line of Credit Facility [Line Items]        
Committed capacity $ 1,500,000,000.0      
Credit facility 2018 [Member] | Line of Credit        
Line of Credit Facility [Line Items]        
Committed capacity $ 700,000,000.0      
Debt instrument, term 4 years      
Debt instrument, maturity date Mar. 29, 2022      
Number of extensions allowed | extension_option 2      
Term of extension 6 months      
Credit facility 2018 [Member] | 2015 Term Loan [Member]        
Line of Credit Facility [Line Items]        
Debt instrument, face amount $ 150,000,000      
Credit facility 2018 [Member] | 2018 Term Loan [Member]        
Line of Credit Facility [Line Items]        
Debt instrument, face amount 250,000,000      
Credit facility 2018 [Member] | 2018 Term Loan A [Member]        
Line of Credit Facility [Line Items]        
Debt instrument, face amount $ 150,000,000      
Credit facility 2018 [Member] | 2018 Term Loan A [Member] | LIBOR [Member]        
Line of Credit Facility [Line Items]        
Basis spread on variable rate (percent) 1.10%      
Credit facility 2018 [Member] | 2018 Term Loan B [Member]        
Line of Credit Facility [Line Items]        
Proceeds from term loan $ 100,000,000      
Credit facility 2015 [Member] | Line of Credit        
Line of Credit Facility [Line Items]        
Committed capacity $ 600,000,000      
Debt instrument, maturity date Jun. 22, 2019