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Common Stock (Tables) | 12 Months Ended
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Dec. 31, 2017
Common Stock. |
Summary of the cost and number of Class A common stock repurchased |
|  | Year Ended December 31, |
|  | 2017 |  | 2016 |
|  | Number of shares |  | Cost of shares |  | Number of shares |  | Cost of shares |
|  | repurchased |  | repurchased |  | repurchased |  | repurchased |
|  | (amounts in millions, except share amount) |
Stock repurchase programs: |  |  |  |  |  |  |  |  |  |  |
July 27, 2015 |  | 277,886 |  |  | 18.2 |  | 501,229 |  |  | 26.8 |
Total |  | 277,886 |  | $ | 18.2 |  | 501,229 |  | $ | 26.8 |

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- Definition Tabular disclosure of an entity's number of shares repurchased and cost of repurchase during the period. + References No definition available. + Details
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