Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors - Noncash Operating, Investing and Financing Activities (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Parent [Member]
Investing activities:
Intercompany return of capital		$ 563.0
Intercompany capital investment		(10,396.2)
Financing activities:
Intercompany capital distribution		(563.0)
Issuer [Member]
Investing activities:
Intercompany return of capital		1,478.0
Intercompany notes issued		(3,800.0)
Intercompany notes proceeds		4,519.8
Intercompany capital investment		(5,434.8)
Financing activities:
Intercompany capital distribution		(563.0)
Intercompany notes borrowing		3,800.0
Intercompany capital receipt		10,396.2
Guarantor Subsidiaries [Member]
Investing activities:
Intercompany return of capital		915.0
Intercompany notes issued	$ (2.3)	(4,519.8)
Intercompany notes proceeds	10.4	4,519.8
Intercompany capital investment	(0.6)	(5,892.3)
Financing activities:
Intercompany capital distribution		(457.5)
Intercompany notes borrowing		457.5
Intercompany notes payments		(457.5)
Intercompany capital receipt		4,977.3
Non-Guarantor Subsidiaries [Member]
Investing activities:
Intercompany notes issued		(8,057.5)
Intercompany notes proceeds		4,257.5
Financing activities:
Intercompany capital distribution		(1,372.5)
Intercompany notes borrowing	2.3	12,119.8
Intercompany notes payments	(10.4)	(12,839.6)
Intercompany capital receipt	0.6	6,349.8
Intercompany dividends paid	(18.6)	(572.4)
Eliminations [Member]
Investing activities:
Intercompany return of capital		(2,956.0)
Intercompany notes issued	2.3	16,377.3
Intercompany notes proceeds	(10.4)	(13,297.1)
Intercompany capital investment	0.6	21,723.3
Financing activities:
Intercompany capital distribution		2,956.0
Intercompany notes borrowing	(2.3)	(16,377.3)
Intercompany notes payments	10.4	13,297.1
Intercompany capital receipt	(0.6)	(21,723.3)
Intercompany dividends paid	$ 18.6	$ 572.4