Related Party Transactions - Additional Information (Details) - The Duchossois Group - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
Jun. 09, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Stock repurchased during period (in shares)	3,000,000	3,000,000
Repurchase price (in dollars per share)	$ 52.93
Stock repurchased and retired during period, value	$ 158.8

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

+ References

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Total cost of shares repurchased divided by the total number of shares repurchased.

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