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Fair Value Measurements - Carrying Value and Fair Value of Debt (Detail) - USD ($)
$ in Millions
Mar. 31, 2020
Dec. 31, 2019
Carrying Value    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total debt $ 2,435.1 $ 2,184.3
Carrying Value | Senior Unsecured Notes [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total debt 2,185.1 2,184.3
Carrying Value | Revolving Credit [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total debt 250.0  
Fair Value    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total debt 2,436.9 2,271.4
Fair Value | Senior Unsecured Notes [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total debt 2,186.9 $ 2,271.4
Fair Value | Revolving Credit [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total debt $ 250.0