Description of the Business - Additional Information (Detail) shares in Millions |
12 Months Ended |
|---|---|
|
Dec. 31, 2017
Segment
shares
| |
| Description Of Business And Basis Of Presentation [Line Items] | |
| Number of reportable segments | Segment | 2 |
| Percentage of common limited partnership interest | 2.59% |
| Class A Common [Member] | |
| Description Of Business And Basis Of Presentation [Line Items] | |
| Class of common limited partnership units designated as class A common units | shares | 8.9 |
| General Partner | |
| Description Of Business And Basis Of Presentation [Line Items] | |
| Percentage of ownership in operating partnership | 97.41% |
| Preferred [Member] | |
| Description Of Business And Basis Of Presentation [Line Items] | |
| Percentage of ownership in operating partnership | 100.00% |