Capital Stock and Derivative Instruments - Schedule of Unamortized Value of Restricted Stock (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	$ 500
Unamortized fair-value - event dependent	6,629
Total unamortized dollar value	7,129	$ 7,700
2nd quarter 2017 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	84
3rd quarter 2017 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	84
4th quarter 2017 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	84
1st quarter 2018 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	77
2nd quarter 2018 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	45
3rd quarter 2018 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	44
4th quarter 2018 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	44
1st quarter 2019 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	$ 38