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Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
May 30, 2018 | Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Unrecognized compensation cost |  | $ 47,131 |  | $ 47,131 |
Total intrinsic value of options exercised |  |  |  | 123,365 |
Aggregate intrinsic value of options exercisable |  | $ 247,517 |  | $ 247,517 |
Market value of Company's common stock (in USD per share) |  | $ 61.10 |  | $ 61.10 |
Weighted average exercise price per share (in USD per share) |  | $ 29.60 |  | $ 29.60 |
Total options outstanding (in shares) |  | 14,040 |  | 14,040 |
Total options exercisable (in shares) |  | 7,857 |  | 7,857 |
Cash dividend declared (in USD per share) | $ 0.30 | $ 0 | $ 0 | $ 0.30 | $ 0.28
Cash dividends declared |  |  |  | $ 47,139 | $ 44,264
Common Stock Buyback |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares purchased and retired (in shares) |  |  |  | 4,419 |
Company purchased, cost |  |  |  | $ 289,536 |
Remaining stock repurchase authorization amount |  | $ 81,102 |  | $ 81,102 |
2014 Plan | Tranche One |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Vesting rate |  |  |  | 50.00% |
2014 Plan | Tranche Two |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Vesting rate |  |  |  | 50.00% |

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