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Investments - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Jul. 19, 2018
Sep. 30, 2020
Sep. 30, 2019
Debt and Equity Securities, FV-NI [Line Items]      
Equity securities   $ 875.3 $ 721.5
PTC      
Debt and Equity Securities, FV-NI [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    
Entity specific transfer restrictions, period 3 years    
Sale of stock, subsequent trading period 90 days    
Gain on fair value of PTC shares   $ 153.9 $ (368.5)
PTC | Minimum      
Debt and Equity Securities, FV-NI [Line Items]      
Percentage of total outstanding common stock, that can be traded in future periods 1.00%    
PTC | Maximum      
Debt and Equity Securities, FV-NI [Line Items]      
Percentage of total outstanding common stock, that can be traded in future periods 2.00%