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Derivative and Other Fair Value Instruments - Additional Information (Details)
 1 Months Ended 12 Months Ended
Nov. 30, 2018
USD ($)
DerivativeInstrument
Feb. 28, 2018
USD ($)
DerivativeInstrument
Aug. 31, 2017
USD ($)
DerivativeInstrument
Oct. 31, 2016
USD ($)
DerivativeInstrument
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Derivative [Line Items]              
Unrealized gain (loss) on interest rate cash flow hedges, pretax, accumulated other comprehensive income (loss)         $ 65,000,000 $ 88,600,000  
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net         $ 20,900,000    
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net             $ (74,000)
2.85% Notes [Member]              
Derivative [Line Items]              
Forward starting swaps settled | DerivativeInstrument       1      
Interest expense       $ 9,000      
Increase (decrease) in charges hedge termination activities       $ 4,600,000      
Debt instrument, term       10 years      
Payments for (proceeds from) hedge, investing activities       $ 4,700,000      
Proceeds from issuance of unsecured debt       500,000,000      
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net       $ (74,000)      
Forward Starting Swaps [Member]              
Derivative [Line Items]              
Proceeds from settlement of derivative instruments $ 16,400,000 $ 1,600,000 $ 1,300,000        
Forward starting swaps settled | DerivativeInstrument 6 2 4        
Interest expense $ 120,000            
Increase (decrease) in charges hedge termination activities (16,500,000) $ (1,600,000) $ (1,300,000)        
Public notes, face value $ 400,000,000 $ 500,000,000 $ 400,000,000        
Debt instrument, term 10 years 10 years 10 years        
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net             $ (74,000)