v3.10.0.1
Property, Plant and Equipment and Other Intangibles (Narrative) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Property, Plant and Equipment [Line Items]      
Interest Costs Threshold For Capitalization Construction In Process $ 500    
Long-term Debt, Weighted Average Interest Rate, over Time 4.80% 4.80% 4.90%
Property, Plant and Equipment, Gross $ 7,628,592 $ 7,235,468  
Depreciation expense $ 214,400 196,300 $ 176,700
Finite-Lived Intangible Asset, Useful Life 20 years    
Amortization of Intangible Assets $ 1,600 400 $ 1,400
Impairments 49,100    
Property, Plant and Equipment, Other Types [Member]      
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Gross 261,075 244,884  
Capitalized Interest [Member] | Property, Plant and Equipment, Other Types [Member]      
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Gross $ 67,600 $ 57,300  
Minimum [Member]      
Property, Plant and Equipment [Line Items]      
Finite-Lived Intangible Asset, Useful Life 7 years    
Maximum [Member]      
Property, Plant and Equipment [Line Items]      
Finite-Lived Intangible Asset, Useful Life 30 years