Annual report pursuant to Section 13 and 15(d)

Debt, Net (Details 3)

v3.10.0.1
Debt, Net (Details 3) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Carrying Amount [Member]    
Debt Instrument [Line Items]    
Long-term debt $ 1,823,909 $ 1,828,333
Carrying Amount [Member] | Unsecured Senior Notes [Member]    
Debt Instrument [Line Items]    
Long-term debt 1,191,046 1,189,249
Carrying Amount [Member] | Other fixed-rate debt [Member]    
Debt Instrument [Line Items]    
Long-term debt 148,308 152,010
Carrying Amount [Member] | Variable-rate debt [Member]    
Debt Instrument [Line Items]    
Long-term debt 484,555 487,074
Estimated Fair Value [Member]    
Debt Instrument [Line Items]    
Long-term debt 1,853,206 1,867,577
Estimated Fair Value [Member] | Unsecured Senior Notes [Member]    
Debt Instrument [Line Items]    
Long-term debt 1,219,603 1,229,398
Estimated Fair Value [Member] | Other fixed-rate debt [Member]    
Debt Instrument [Line Items]    
Long-term debt 147,106 152,485
Estimated Fair Value [Member] | Variable-rate debt [Member]    
Debt Instrument [Line Items]    
Long-term debt $ 486,497 $ 485,694