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Computation of Earnings Per Common Share - Narratives (Details) - $ / shares | 6 Months Ended |  |  |
--- | --- | --- | --- | ---
Jan. 27, 2018 | Jul. 29, 2017 | Jul. 30, 2016 | Sep. 15, 2015
Shares used in computing earnings per common share: |  |  |  |
Adoption of accounting principled effect on diluted shares | 177,575 |  |  |
Weighted average stock price (usd per share) | $ 106.11 |  |  |
Convertible Note Hedge |  |  |  |
Shares used in computing earnings per common share: |  |  |  |
Debt instrument, convertible, conversion price (per share) | $ 96.89 |  |  | $ 96.89
0.75% Convertible Senior Notes Due 2021 |  |  |  |
Shares used in computing earnings per common share: |  |  |  |
Debt, interest rate (in percent) | 0.75% | 0.75% | 0.75% |
Debt instrument, convertible, conversion price (per share) |  |  |  | 96.89
Class of warrant or right, exercise price of warrants or rights (per warrant) | $ 130.43 |  |  | $ 130.43

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