XML 56 R43.htm IDEA: XBRL DOCUMENT v3.7.0.1
Fair Value Measurements - Summary of Financial Assets and Liabilities Not Carried at Fair Value (Details) - Level 2 - USD ($)
$ in Millions
Mar. 31, 2017
Dec. 31, 2016
Carrying Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions    
Senior notes $ 945.3 $ 945.1
Convertible securities 308.0 307.5
Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions    
Senior notes 962.2 936.0
Convertible securities $ 489.5 $ 466.9