v3.8.0.1

Equity-Based Compensation (Tables) | 9 Months Ended
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Sep. 30, 2017
Equity-Based Compensation |
Summary of restricted unit and phantom unit awards activity |
|  |  |  | Weighted average |  | Aggregate |
|  | Number of units |  | grant date fair value |  | intrinsic value (in thousands) |
Total awarded and unvested—December 31, 2016 |  | 1,331,961 |  | $ | 27.31 |  | $ | 41,131 |
Granted |  | 377,660 |  | $ | 32.52 |  |  |  |
Vested |  | (73,080) |  | $ | 21.34 |  |  |  |
Forfeited |  | (78,584) |  | $ | 28.75 |  |  |  |
Total awarded and unvested—September 30, 2017 |  | 1,557,957 |  | $ | 28.78 |  | $ | 49,122 |

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- Definition Represents the phantom and restricted unit award activity under the equity based compensation plan. + References No definition available. + Details
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Namespace Prefix: | am_
Data Type: | nonnum:textBlockItemType
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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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