Mortgage Loans - Loan Commitments and Related Derivatives (Details) - Financial Services [Member] - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015
Interest rate lock commitments [Member]
Derivative [Line Items]
Notional amounts of instruments	$ 372.9	$ 370.9
Best-efforts and mandatory commitments [Member]
Derivative [Line Items]
Notional amounts of instruments	32.6	37.7
Hedging Instruments related to IRLCs [Member]
Derivative [Line Items]
Notional amounts of instruments	$ 301.3	$ 297.2