XML 129 R112.htm IDEA: XBRL DOCUMENT v3.20.4
Financial Instruments - Fair Value of Debt Instruments (Details) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Investments, All Other Investments [Abstract]    
Estimated aggregate fair value $ 2,633.3 $ 2,384.6
Long-term debt, gross $ 2,320.3 $ 2,334.4