Fair Value Measurements - Additional Information (Detail) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of the embedded derivatives	$ 0	$ 0
2017 Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of principal amount	16,492,000	25,769,000
2022 Notes | Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of the embedded derivatives	$ 0	$ 0