Shareholders' Equity (Narrative) (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Equity [Abstract] | |||
| Stock repurchase plan, authorized amount | $ 700,000,000 | ||
| Aggregate shares repurchased under stock repurchase plan | 21,658,035 | ||
| Stock repurchased to date, value | $ 562,064,000 | ||
| Stock Repurchased During Period, Value | $ 35,542,000 | $ 11,000 | $ 70,068,000 |
| X | ||||||||||
- Definition Number of shares that have been repurchased to date under the program. No definition available.
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| X | ||||||||||
- Definition Equity impact of the value of stock that has been repurchased to date and has not been retired and is not held in treasury. Some state laws may mandate 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. No definition available.
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of stock repurchase plan authorized. No definition available.
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| X | ||||||||||
- Definition Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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