Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Statement of Financial Position [Abstract]
Investments, at fair value	$ 588.3	$ 504.8
Preferred stock, par value	$ 1.00	$ 1.00
Preferred stock, shares authorized	1,000,000	1,000,000
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares outstanding	501,807,677	495,116,677
Common stock, shares issued	501,807,677	495,116,677