Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares shares in Millions |
Sep. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Statement Of Financial Position [Abstract] | ||
| Common shares, par value | $ 0.0005 | $ 0.0005 |
| Common shares, shares authorized | 2,000.0 | 2,000.0 |
| Common shares, shares outstanding | 146.1 | 164.7 |
| Treasury stock shares, at cost | 10.0 | 10.0 |
| X | ||||||||||
- Definition Face amount or stated value per share of common stock. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Number of previously issued common shares repurchased by the issuing entity and held in treasury. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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