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Equity and Distributions - Summary of Changes in Number of Outstanding Units (Detail)
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12 Months Ended | |||
|---|---|---|---|---|
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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| Summary Of Changes In Number Of Outstanding Units [Abstract] | ||||
| Beginning balance | 61,300 | 34,317 | 22,044 | |
| General partner units issued | 25,497 | 26,983 | 12,273 | |
| Ending balance | 86,797 | 61,300 | 34,317 | |
| Limited Partners Common Units [Member] | ||||
| Summary Of Changes In Number Of Outstanding Units [Abstract] | ||||
| Beginning balance | 55,877,831 | 28,921,903 | 16,661,294 | |
| Common units issued | 24,840,000 | 26,450,000 | 11,975,000 | |
| Restricted common units issued | 684,954 | 524,717 | 287,943 | |
| Restricted common units forfeited | (38,294) | (11,734) | (2,334) | |
| Restricted common units repurchased | (42,587) | (7,055) | ||
| Common units repurchased under repurchase program | (899,912) | |||
| Ending balance | 80,421,992 | 55,877,831 | 28,921,903 | |
| Subordinated Units [Member] | ||||
| Summary Of Changes In Number Of Outstanding Units [Abstract] | ||||
| Beginning balance | 5,360,912 | |||
| Ending balance | 5,360,912 | 5,360,912 | 5,360,912 | 5,360,912 |