CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jan. 10, 2018	Jun. 30, 2018	Jan. 11, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.001	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)		199,300,000.0		199,300,000.0
Common stock, shares issued (in shares)		108,600,000		107,100,000
Common stock, shares outstanding (in shares)		91,400,000		89,900,000
Treasury stock, at cost, shares held (in shares)		17,200,000		17,200,000
Shares of surviving corporation (in shares)	1

Number of shares of equity interests issued or issuable to acquire entity.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
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Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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-Topic 505
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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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