Investments (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	$ 50.7	$ 61.8
Available-for-Sale Securities, Gross Unrealized Gain	0.3	0.0
Available-for-Sale Securities, Gross Unrealized Loss	(0.1)	0.0
Available-for-Sale Securities	50.9	61.8
Current [Member] \| U.S. corporate bonds [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis		11.2
Available-for-Sale Securities, Gross Unrealized Gain		0.0
Available-for-Sale Securities, Gross Unrealized Loss		0.0
Available-for-Sale Securities		11.2
Noncurrent [Member] \| Marketable equity securities [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis		6.2
Available-for-Sale Securities, Gross Unrealized Gain		0.0
Available-for-Sale Securities, Gross Unrealized Loss		0.0
Available-for-Sale Securities		6.2
Noncurrent [Member] \| Federal government securities [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	31.3	32.0
Available-for-Sale Securities, Gross Unrealized Gain	0.2	0.0
Available-for-Sale Securities, Gross Unrealized Loss	0.0	0.0
Available-for-Sale Securities	31.5	32.0
Noncurrent [Member] \| U.S. corporate bonds [Member]
Schedule of Available-for-Sale Securities
Available-for-sale Securities, Amortized Cost Basis	19.4	12.4
Available-for-Sale Securities, Gross Unrealized Gain	0.1	0.0
Available-for-Sale Securities, Gross Unrealized Loss	(0.1)	0.0
Available-for-Sale Securities	19.4	12.4
Fair Value, Measurements, Recurring [Member]
Schedule of Available-for-Sale Securities
Available-for-Sale Securities	$ 50.9	$ 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

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

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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.

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