Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Document Period End Date	Dec. 31, 2020
Property, Plant and Equipment, Useful Life	40 years
Other Asset Impairment Charges	$ 5.0	$ 4.0	$ 5.0
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	116.0	99.0
Property, Plant and Equipment, Gross	260.0	244.0
Depreciation	17.0	18.0	18.0
Goodwill	7.0
Present Value of Future Insurance Profits, Net	4.0	5.0
Amortization of Value of Business Acquired (VOBA)	0.5	0.7	0.4
Values Of Business Acquired Distribution Agreements And Customer Relationships	25.0	33.0
Accumulated Amortization Of Values Of Business Acquired Distribution Agreements And Customer Relationships	96.0	88.0
Amortization Of Values Of Business Acquired Distribution Agreements And Customer Relationships	8.0	8.0	8.0
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	7.0
Finite-Lived Intangible Assets, Amortization Expense, Year Two	6.0
Finite-Lived Intangible Assets, Amortization Expense, Year Three	6.0
Finite-Lived Intangible Assets, Amortization Expense, Year Four	6.0
Capitalized Computer Software, Net	147.0	151.0
Capitalized Computer Software, Amortization	$ 32.0	31.0	$ 27.0
Value of Customer Relationships Acquired [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Value of Distribution Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization Of Values Of Business Acquired Distribution Agreements And Customer Relationships	$ 12.0	$ 8.0
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	4.0
Finite-Lived Intangible Assets, Amortization Expense, Year Two	4.0
Finite-Lived Intangible Assets, Amortization Expense, Year Three	4.0
Finite-Lived Intangible Assets, Amortization Expense, Year Four	4.0
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 4.0
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Collateral Obtained Percent Of Fair Value Reverse Repurchase Agreements	100.00%
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Collateral Obtained Percent Of Fair Value Reverse Repurchase Agreements	105.00%