Fair Value Measurements - Schedule of Reconciliation of Changes In Fair Value of Convertible Debentures (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Feb. 21, 2020	Dec. 31, 2019	Feb. 21, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 13,642
Conversion		$ (21,164)	$ (13,642)	$ (21,200)
Convertible Debentures [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	13,642
Fair value adjustments	7,522
Conversion	$ (21,164)