Mortgage Loans - Loan Commitments and Related Derivatives (Details) - USD ($) $ in Millions |
Mar. 31, 2018 |
Sep. 30, 2017 |
---|---|---|
Interest rate lock commitments [Member] | ||
Derivative [Line Items] | ||
Notional amounts of instruments | $ 719.9 | $ 446.2 |
Best-efforts and mandatory commitments [Member] | ||
Derivative [Line Items] | ||
Notional amounts of instruments | 58.6 | 26.9 |
Hedging Instruments related to IRLCs [Member] | ||
Derivative [Line Items] | ||
Notional amounts of instruments | $ 601.1 | $ 389.3 |