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Earnings Per Share - Treasury Stock Narrative (Details) - USD ($) | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Apr. 08, 2016 | Feb. 29, 2016 | Feb. 29, 2016 | Sep. 30, 2015 | Aug. 04, 2015 | Jan. 13, 2015
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |
Shares |  | 1,188,000 | 5,662,000 | 5,900,000 |  |
Average price per share (in dollars per share) |  | $ 84.15 | $ 85.29 | $ 84.07 |  |
Purchase price |  | $ 99,997,000 | $ 482,915,000 | $ 500,000,000 |  |
Employee payroll taxes due on restricted stock |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |
Shares |  |  | 200,000 |  |  |
Average price per share (in dollars per share) |  |  | $ 85.62 |  |  |
Purchase price |  | $ 100,000 | $ 19,500,000 |  |  |
January 13, 2015 |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |
Share buyback program, authorized amount |  |  |  |  |  | $ 500,000,000.0
Shares |  | 0 | 3,078,000 |  |  |
Average price per share (in dollars per share) |  | $ 0.00 | $ 85.44 |  |  |
Purchase price |  | $ 0 | $ 262,937,000 |  |  |
August 4, 2015 |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |
Share buyback program, authorized amount |  |  |  |  | $ 500,000,000.0 |
Shares |  | 1,188,000 | 2,584,000 |  |  |
Average price per share (in dollars per share) |  | $ 84.15 | $ 85.11 |  |  |
Purchase price |  | $ 99,997,000 | $ 219,978,000 |  |  |
Subsequent Event |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |
Shares | 500,000 |  |  |  |  |
Purchase price | $ 47,800,000 |  |  |  |  |
Subsequent Event | Employee payroll taxes due on restricted stock |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |
Shares | 0 |  |  |  |  |

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