Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Income [Abstract]
Net Income	$ 114.5us-gaap_ProfitLoss	$ 217.7us-gaap_ProfitLoss	$ 103.4us-gaap_ProfitLoss
Unrealized Holding Gains (Losses)	234.6	(362.8)	96.7
Foreign Currency Translation Adjustments	(1.0)	0.2	1.6
Decrease (Increase) in Net Unrecognized Postretirement Benefit Costs	(98.5)	86.6	(13.2)
Other Comprehensive Income (Loss) Before Income Taxes	135.1	(276.0)	85.1
Other Comprehensive Income Tax Benefit (Expense)	(47.7)us-gaap_OtherComprehensiveIncomeLossTax	98.6us-gaap_OtherComprehensiveIncomeLossTax	(30.4)us-gaap_OtherComprehensiveIncomeLossTax
Other Comprehensive Income (Loss)	87.4	(177.4)	54.7
Total Comprehensive Income	$ 201.9	$ 40.3	$ 158.1

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount before tax, after reclassification adjustments of other comprehensive income (loss).

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Amount before tax, after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount before tax, after reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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