Investment Securities (Cost and Amortized Cost Maturity Schedule) (Details) $ in Millions	Dec. 31, 2018 USD ($)
Trading Securities by Maturity Cost or Amortized Cost
Cost of Amortized Cost	$ 1,088.1
Trading Securities by Maturity, Fair Value
Common equity securities	1,077.5
Fixed Maturities and Convertible Fixed Maturities Excluding A B S M B S and Preferred Stock
Trading Securities by Maturity Cost or Amortized Cost
Due in one year or less	84.8
Due after one year through five years	500.8
Due after five years through ten years	222.4
Due after ten years	144.0
Trading Securities by Maturity, Fair Value
Due in one year or less	84.4
Due after one year through five years	496.2
Due after five years through ten years	218.0
Due after ten years	145.4
Mortgage and asset-backed securities
Trading Securities by Maturity Cost or Amortized Cost
Mortgage and asset-backed securities	136.1
Trading Securities by Maturity, Fair Value
Mortgage and asset-backed securities	$ 133.5

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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This item represents the carrying value of debt securities which are expected to mature after five years and through ten years from the balance sheet date classified as trading.

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