Mortgage Loans - Loan Commitments and Related Derivatives (Details) - Financial Services and Other [Member] - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Interest rate lock commitments [Member]
Derivative [Line Items]
Notional amounts of instruments	$ 643.8	$ 467.6
Best-efforts and mandatory commitments [Member]
Derivative [Line Items]
Notional amounts of instruments	55.0	37.2
Hedging Instruments related to IRLCs [Member]
Derivative [Line Items]
Notional amounts of instruments	$ 545.2	$ 385.5