Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) yr	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Mortgage Banking [Abstract]
Mortgage servicing rights	$ 376.4	$ 193.8
Mortgage-backed Securities Held-to-maturity, Fair Value Disclosure	$ 423.7	246.8
Real Estate Investments, Net [Abstract]
Minimum ownership percentage in real estate ventures (in hundredths)	1.00%
Maximum ownership percentage in real estate ventures (in hundredths)	10.00%
Foreign Currency Translation [Abstract]
Net foreign currency gains (losses)	$ (2.4)	(4.1)	$ (4.8)
Bank Servicing Fees.	63.0	49.6	$ 43.3
Operating Lease, Right-of-Use Asset	804.4	0.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 404.2	$ 356.9
Share-based Payment Arrangement [Member]
Share Based Compensation Arrangement By Share Based Payment Award Sum Of Age Plus Years Of Service Minimum \| yr	65

Revenue from servicing real estate mortgages held by others.

No definition available.

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- Definition

The maximum percentage ownership of common stock or equity participation in the investee under the equity method of accounting.

+ References

No definition available.

+ Details

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- Definition

The minimum percentage ownership of common stock or equity participation in the investee under the equity method of accounting.

+ References

No definition available.

+ Details

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- Definition

Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

+ References

No definition available.

+ Details

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- Definition

This element represent the minimum sum of age plus years of service with the company to be eligible for receipt of retirement benefits upon departure from the company.

+ References

No definition available.

+ Details

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- Definition

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
-Paragraph 1
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- References

No definition available.

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- Definition

Amount of investment in equity method investee and investment in and advance to affiliate.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as held-to-maturity.

+ References

No definition available.

+ Details

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- References

No definition available.

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Balance Type:	na
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- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

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- References

No definition available.

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