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v3.23.1

Marketable Securities (Tables) | 3 Months Ended
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Mar. 31, 2023
Investments Debt And Equity Securities [Abstract] |
Schedule of Marketable Securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | Cost or | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | amortized | ​ | Unrealized
​ | ​ | Market value | ​ | cost | ​ | loss, net
​ | ​ | (In millions)
December 31, 2022: |  | ​ |  |  | ​ |  |  | ​ |
Current assets | ​ | $ | 75.1 | ​ | $ | 75.7 | ​ | $ | (.6)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Noncurrent assets | ​ | $ | 1.2 | ​ | $ | 1.2 | ​ | $ | —
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
March 31, 2023: | ​ |  |  | ​ |  |  | ​ |  |
Current assets | ​ | $ | 101.0 | ​ | $ | 101.5 | ​ | $ | (.5)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Noncurrent assets | ​ | $ | 1.6 | ​ | $ | 1.6 | ​ | $ | —
​

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- Definition Tabular disclosure of marketable securities. This may consist of investments in certain debt and equity securities, short-term investments and other assets. + References No definition available. + Details
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