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Fair Value Measurements (Details) - USD ($)
Jun. 30, 2017
Dec. 31, 2016
Fair Value, Measurements, Recurring | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents and investments $ 0 $ 0
Carrying value    
Fair Value of Financial Instruments [Abstract]    
Debt 2,179,100,000 2,215,300,000
Fair Value | Level 2    
Fair Value of Financial Instruments [Abstract]    
Debt $ 2,237,500,000 $ 2,275,500,000