XML 76 R52.htm IDEA: XBRL DOCUMENT v3.8.0.1
Borrowings (Interest Rate Ranges, Maturity and Balance of Indebtedness) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 3.60%  
Total outstanding debt $ 4,500,000 $ 4,499,700
Debt Instrument, Maturity Date Mar. 11, 2022  
Unsecured Debt    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 3.50%  
Total outstanding debt $ 3,525,765  
Debt Instrument, Maturity Date Dec. 19, 2022  
Secured Debt [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 3.80%  
Debt Instrument, Maturity Date Sep. 13, 2019  
Variable Rate Debt [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 2.30%  
Unsecured Debt $ 300,000  
Variable Rate Debt [Member] | Unsecured Debt    
Debt Instrument [Line Items]    
Debt Instrument, Maturity Date Aug. 29, 2020  
Secured Debt [Member] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Total outstanding debt $ 976,292  
Fixed Rate Debt    
Debt Instrument [Line Items]    
Total outstanding debt $ 3,724,800 3,838,300
Fixed Rate Debt | Taxable Secured    
Debt Instrument [Line Items]    
Average Interest Rates 3.97%  
Total outstanding debt $ 882,800 1,128,300
Fixed Rate Debt | Unsecured Debt    
Debt Instrument [Line Items]    
Average Interest Rates 3.97%  
Total outstanding debt $ 2,292,000 1,860,000
Fixed Rate Debt | Interest Rate Swap    
Debt Instrument [Line Items]    
Debt Instrument Maturity Year 2018  
Average Interest Rates 2.96%  
Total outstanding debt $ 550,000 850,000
Fixed Rate Debt | Minimum | Taxable Secured    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate 0.0300  
Debt Instrument Maturity Year 2018  
Fixed Rate Debt | Minimum | Unsecured Debt    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate .0338  
Debt Instrument Maturity Year 2018  
Fixed Rate Debt | Minimum | Interest Rate Swap    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate .0245  
Fixed Rate Debt | Maximum | Taxable Secured    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate 0.0549  
Debt Instrument Maturity Year 2025  
Fixed Rate Debt | Maximum | Unsecured Debt    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate 0.0557  
Debt Instrument Maturity Year 2027  
Fixed Rate Debt | Maximum | Interest Rate Swap    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate 0.0355  
Variable Rate [Domain] | Secured Debt [Member]    
Debt Instrument [Line Items]    
Interest rate, stated percentage 1.76%  
Variable Rate [Domain] | Interest Rate Cap    
Debt Instrument [Line Items]    
Interest rate, stated percentage 1.76%  
Variable Rate Debt    
Debt Instrument [Line Items]    
Total outstanding debt $ 790,000 650,000
Variable Rate Debt | Taxable Secured    
Debt Instrument [Line Items]    
Debt Instrument Maturity Year [1] 2018  
Average Interest Rates [1] 1.76%  
Total outstanding debt [1] $ 55,000 110,000
Variable Rate Debt | Unsecured Debt    
Debt Instrument [Line Items]    
Average Interest Rates [1] 2.41%  
Total outstanding debt [1] $ 710,000 490,000
Variable Rate Debt | Interest Rate Cap    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate [1] 0.0176  
Debt Instrument Maturity Year [1] 2018  
Average Interest Rates [1] 1.76%  
Total outstanding debt [1] $ 25,000 50,000
Variable Rate Debt | Minimum | Taxable Secured    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate [1] .0176  
Variable Rate Debt | Minimum | Unsecured Debt    
Debt Instrument [Line Items]    
Debt Instrument Maturity Year [1] 2020  
Interest rate, stated percentage [1] 2.31%  
Variable Rate Debt | Maximum | Taxable Secured    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Basis for Effective Rate [1] .0176  
Variable Rate Debt | Maximum | Unsecured Debt    
Debt Instrument [Line Items]    
Debt Instrument Maturity Year [1] 2021  
Interest rate, stated percentage [1] 2.47%  
Fair Market Value Adjustment and Debt Issuance Cost [Member]    
Debt Instrument [Line Items]    
Total outstanding debt $ (12,700) $ 11,400
[1] Amounts are adjusted to reflect interest rate swap and cap agreements in effect at December 31, 2017, and 2016, respectively, which results in paying fixed interest payments over the terms of the interest rate swaps and on changes in interest rates above the strike rate of the cap.