Fair Value Measurements, Available-for-sale Securities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Market Value	$ 8.7us-gaap_AvailableForSaleSecurities	$ 14.3us-gaap_AvailableForSaleSecurities
Cost Basis		11.9
Gross Unrealized Gains		2.5
Gross Unrealized Losses		0.1
Fair value of available-for-sale investments contributed to defined benefit plans		27.1us-gaap_TransferOfInvestments
Available-for-sale Securities, Gross Realized Gains	2.0	11.0
Mutual Fund and Unit Trust Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	8.7	9.8
Cost Basis	6.5	7.3
Gross Unrealized Gains	2.2	2.5
Gross Unrealized Losses	0	0
Auction Rate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value		4.5
Cost Basis		4.6
Gross Unrealized Gains		0
Gross Unrealized Losses		$ 0.1

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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Value of investments transferred from the entity's investments in noncash transactions.

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