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Investments - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Jul. 19, 2018
Sep. 30, 2018
Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]      
Equity securities   $ 1,090.0 $ 877.3
PTC      
Subsidiary, Sale of Stock [Line Items]      
Number of shares purchased (in shares) 10,582,010    
Purchase of stock price (usd per share) $ 94.50    
Consideration paid to purchase stock $ 1,000.0    
Purchase of stock purchase period 3 years    
Sale of stock, subsequent trading period 90 days    
Equity securities   877.3  
Trading investment, unrealized gain (loss)   $ (212.7)  
PTC | Minimum      
Subsidiary, Sale of Stock [Line Items]      
Percentage of total outstanding common stock, that can be traded in future periods 1.00%    
PTC | Maximum      
Subsidiary, Sale of Stock [Line Items]      
Percentage of total outstanding common stock, that can be traded in future periods 2.00%