Financial Restructuring and Elimination of Going Concern Assumption - Additional Information (Detail) - USD ($) $ in Millions	Feb. 24, 2017	Dec. 31, 2016	Dec. 31, 2015
Financial Restructuring And Elimination Of Going Concern Assumption [Line Items]
Long-term debt		$ 3.8	$ 55.0
Short-term debt		38.2	35.5
Cash		10.0	5.7
Working capital deficit		$ 17.3	24.5
Subsequent Event [Member]
Financial Restructuring And Elimination Of Going Concern Assumption [Line Items]
Repayments of short-term debt	$ 2.7
Subsequent Event [Member] | Thrace Basin Natural Gas (Turkiye) Corporation [Member]
Financial Restructuring And Elimination Of Going Concern Assumption [Line Items]
Gross proceeds on sale of ownership interests	20.9
Net cash proceeds on sale of ownership interests	16.3
Escrow deposit	$ 3.1
13.0% Convertible Notes Due in 2017 [Member] | Convertible Debt [Member]
Financial Restructuring And Elimination Of Going Concern Assumption [Line Items]
Debt instrument interest rate stated percentage		13.00%
Senior Credit Facility [Member]
Financial Restructuring And Elimination Of Going Concern Assumption [Line Items]
Borrowing base deficiency			$ 15.5