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Derivative and Other Fair Value Instruments - Additional Information (Details)
 1 Months Ended 12 Months Ended
Aug. 31, 2017
USD ($)
DerivativeInstrument
Oct. 31, 2016
USD ($)
DerivativeInstrument
May 31, 2015
USD ($)
DerivativeInstrument
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Derivative [Line Items]            
Unrealized gain (loss) on interest rate cash flow hedges, pretax, accumulated other comprehensive income (loss)       $ 88,600,000 $ 113,900,000  
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net       $ 21,200,000    
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net         (74,000) $ (3,033,000)
Forward Starting Swaps [Member]            
Derivative [Line Items]            
Proceeds from settlement of derivative instruments $ 1,300,000          
Forward starting swaps settled | DerivativeInstrument 4          
Public notes, face value $ 400,000,000          
Debt instrument, term 10 years          
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net         $ (74,000) $ (3,033,000)
2.85% Notes [Member]            
Derivative [Line Items]            
Forward starting swaps settled | DerivativeInstrument   1        
Payments for (proceeds from) hedge, investing activities   $ 4,700,000        
Proceeds from issuance of unsecured debt   500,000,000        
Interest expense   9,000        
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net   (74,000)        
Charges hedge termination activities   $ 4,600,000        
3.375% Notes [Member]            
Derivative [Line Items]            
Forward starting swaps settled | DerivativeInstrument     9      
Payments for (proceeds from) hedge, investing activities     $ 15,100,000      
Proceeds from issuance of unsecured debt     450,000,000      
Interest expense     1,200,000      
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net     (30,000)      
Charges hedge termination activities     $ 13,900,000