Investments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	$ 58.8	$ 61.8
Available-for-Sale Securities, Gross Unrealized Gain	0.3	0
Available-for-Sale Securities, Gross Unrealized Loss	(0.5)	0
Available-for-Sale Securities	58.6us-gaap_AvailableForSaleSecurities	61.8us-gaap_AvailableForSaleSecurities
Current [Member] \| Federal government securities [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	5.6
Available-for-Sale Securities, Gross Unrealized Gain	0
Available-for-Sale Securities, Gross Unrealized Loss	0
Available-for-Sale Securities	5.6
Current [Member] \| U.S. corporate bonds [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	3.4	11.2
Available-for-Sale Securities, Gross Unrealized Gain	0	0
Available-for-Sale Securities, Gross Unrealized Loss	0	0
Available-for-Sale Securities	3.4	11.2
Noncurrent [Member] \| Marketable equity securities [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	6.2	6.2
Available-for-Sale Securities, Gross Unrealized Gain	0	0
Available-for-Sale Securities, Gross Unrealized Loss	(0.5)	0
Available-for-Sale Securities	5.7	6.2
Noncurrent [Member] \| Federal government securities [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	28.0	32.0
Available-for-Sale Securities, Gross Unrealized Gain	0.2	0
Available-for-Sale Securities, Gross Unrealized Loss	0	0
Available-for-Sale Securities	28.2	32.0
Noncurrent [Member] \| U.S. corporate bonds [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	15.6	12.4
Available-for-Sale Securities, Gross Unrealized Gain	0.1	0
Available-for-Sale Securities, Gross Unrealized Loss	0	0
Available-for-Sale Securities	15.7	12.4
Fair Value, Measurements, Recurring [Member]
Schedule of Available-for-Sale Securities
Available-for-Sale Securities	$ 58.6	$ 61.8

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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