Stockholders' Equity - Restricted Stock Awards, Restricted Stock Units and Performance-Based Restricted Stock Units - Additional Information (Detail) - Inducement Award Performance-Based Restricted Stock Units [Member]		9 Months Ended
	Aug. 23, 2017 USD ($) Tranche shares	Dec. 31, 2017 Tranche shares	Apr. 24, 2017 shares
Class Of Stock [Line Items]
Number of tranches | Tranche	5
Award vesting percentage		0.00%
Number of tranches vested | Tranche		0
Grant date fair values of tranches | $	$ 393,000
Stock units expected to vest		50,117
Maximum [Member]
Class Of Stock [Line Items]
Number of shares allocated	208,822
Share-based Compensation Award, Tranche One [Member]
Class Of Stock [Line Items]
Award vesting percentage	20.00%
Stock units vesting year	2018
Share-based Compensation Award, Tranche One [Member] | Minimum [Member]
Class Of Stock [Line Items]
Award vesting percentage	0.00%
Share-based Compensation Award, Tranche One [Member] | Maximum [Member]
Class Of Stock [Line Items]
Award vesting percentage	120.00%
Share-based Compensation Award, Tranche Two [Member]
Class Of Stock [Line Items]
Award vesting percentage	20.00%
Stock units vesting year	2019
Share-based Compensation Award, Tranche Two [Member] | Minimum [Member]
Class Of Stock [Line Items]
Award vesting percentage	0.00%
Share-based Compensation Award, Tranche Two [Member] | Maximum [Member]
Class Of Stock [Line Items]
Award vesting percentage	120.00%
Share-based Compensation Award, Tranche Three [Member]
Class Of Stock [Line Items]
Award vesting percentage	20.00%
Stock units vesting year	2020
Share-based Compensation Award, Tranche Three [Member] | Minimum [Member]
Class Of Stock [Line Items]
Award vesting percentage	0.00%
Share-based Compensation Award, Tranche Three [Member] | Maximum [Member]
Class Of Stock [Line Items]
Award vesting percentage	120.00%
Share Based Compensation Award Tranche Four [Member]
Class Of Stock [Line Items]
Award vesting percentage	20.00%
Stock units vesting year	2021
Share Based Compensation Award Tranche Four [Member] | Minimum [Member]
Class Of Stock [Line Items]
Award vesting percentage	0.00%
Share Based Compensation Award Tranche Four [Member] | Maximum [Member]
Class Of Stock [Line Items]
Award vesting percentage	120.00%
Share Based Compensation Award Tranche Five [Member]
Class Of Stock [Line Items]
Award vesting percentage	20.00%
Stock units vesting year	2020
Share Based Compensation Award Tranche Five [Member] | Minimum [Member]
Class Of Stock [Line Items]
Award vesting percentage	0.00%
Share Based Compensation Award Tranche Five [Member] | Maximum [Member]
Class Of Stock [Line Items]
Award vesting percentage	120.00%
Future Year [Member]
Class Of Stock [Line Items]
Award vesting percentage		120.00%
CEO [Member]
Class Of Stock [Line Items]
Number of shares allocated			208,822