Capital Stock and Derivative Instruments - Schedule of Unamortized Value of Restricted Stock (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	$ 641
Unamortized fair-value - event dependent	7,086
Total unamortized dollar value	7,727	$ 10,000	$ 1,200
1st quarter 2017 [Member]
Amortization Expense [Line Items]
Unamortized fair value subject to vesting schedule	140
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	78
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