Other Assets, Net - Additional Information (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Indefinite-lived Intangible Assets [Line Items] | |||
| Amortization expense related to deferred debt issuance costs | $ 4,000 | $ 3,600 | $ 4,800 |
| Cost of products sold of natural gas transportation assets | 2,179,089 | 3,188,924 | 4,755,031 |
| Estimated future expense of net natural gas transportation assets for 2017 | 1,700 | ||
| Estimated future expense of net natural gas transportation assets for 2018 | 100 | ||
| Natural gas | |||
| Indefinite-lived Intangible Assets [Line Items] | |||
| Cost of products sold of natural gas transportation assets | 6,500 | 13,400 | 21,900 |
| Provision for inventory write-down | 1,600 | $ 3,600 | 13,600 |
| Metromedia Energy | |||
| Indefinite-lived Intangible Assets [Line Items] | |||
| Natural gas transportation assets | 8,000 | 39,400 | |
| Natural gas transportation liabilities | $ 2,400 | $ 1,500 | |