Unconsolidated Investments - Schedule of Projects Accounted under Equity Method of Accounting (Detail) - USD ($) $ in Thousands |
Sep. 30, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Schedule of Equity Method Investments [Line Items] | ||
| Unconsolidated investments | $ 303,833 | $ 233,294 |
| South Kent [Member] | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Unconsolidated investments | $ 3,732 | $ 1,537 |
| Percentage of ownership | 50.00% | 50.00% |
| Grand [Member] | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Unconsolidated investments | $ 5,758 | $ 3,459 |
| Percentage of ownership | 45.00% | 45.00% |
| K2 [Member] | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Unconsolidated investments | $ 102,019 | $ 97,051 |
| Percentage of ownership | 33.30% | 33.30% |
| Armow [Member] | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Unconsolidated investments | $ 133,063 | $ 131,247 |
| Percentage of ownership | 50.00% | 50.00% |
| PEGH2 [Member] | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Unconsolidated investments | $ 59,261 | $ 0 |
| Percentage of ownership | 20.20% |