Investments - Current and Noncurrent (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
As reported on the consolidated balance sheets:
Current marketable investments	$ 79.6	$ 122.0
Noncurrent marketable investments	2.3	38.0
Total marketable investments	$ 81.9	$ 160.0

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, not expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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