Share-Based Compensation - Schedule of Deferred Stock Units to be Settled in Shares (Detail) shares in Thousands	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning balance of Outstanding, Deferred Stock Units to be Settled in Shares | shares	76	[1]
Granted, Deferred Stock Units to be Settled in Shares | shares	0
Vested, Deferred Stock Units to be Settled in Shares | shares	(3)	[2]
Forfeited, Deferred Stock Units to be Settled in Shares | shares	0
Ending balance of Outstanding, Deferred Stock Units to be Settled in Shares | shares	73	[1]
Beginning balance of Outstanding, Weighted Average Grant-Date Fair Value Per Unit | $ / shares	$ 4.44	[1]
Granted, Weighted Average Grant-Date Fair Value Per Unit | $ / shares	0
Vested, Weighted Average Grant-Date Fair Value Per Unit | $ / shares	5.56	[2]
Forfeited, Weighted Average Grant-Date Fair Value Per Unit | $ / shares	0
Ending balance of Outstanding, Weighted Average Grant-Date Fair Value Per Unit | $ / shares	$ 4.39	[1]

[1] Includes vested but unreleased awards. These awards are included in total outstanding awards until they are released under the terms of the agreement.

[2] Includes previously vested awards which were released during the current period.