Mortgage Loans Mortgage Loans Held for Sale (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Mortgage Loans on Real Estate [Abstract]
Mortgage loans held for sale	$ 622.2		$ 796.4
Mortgage loans held for sale, outstanding principal amount	602.1		$ 776.1
Payments for Origination of Mortgage Loans Held-for-sale	1,600.0	$ 1,600.0
Proceeds from Sale of Mortgage Loans Held-for-sale	1,800.0	1,600.0
Gain (Loss) on Sales of Loans, Net	$ 59.9	$ 57.0
Concentration Risk, Percentage	94.00%
Percentage Of Mortgage Loans Sold To Major Purchaser	35.00%

The percentage of mortgage loans sold to major purchasers during the period.

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

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-Publisher FASB
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- Definition

The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section S99
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-Subparagraph (SX 210.9-04.13(h))
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-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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- Definition

Amount, after allowance for bad debt, of mortgage loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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- References

No definition available.

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- Definition

The amount of cash paid for the origination of mortgages that are held for sale.

+ References

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- Definition

This is the principal amount outstanding for loans which are in the process of being securitized as of the date of the statement of financial position (across all types of loans).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82924980&loc=d3e107314-111719

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- Definition

The cash inflow from sales of loans that are secured with real estate mortgages and are held with the intention to resell in the near future.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

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