Earnings per Share - Calculation of Earnings (Loss) per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended						9 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Line Items]
Net income (loss)		$ 5,157	$ 18,641	$ (31,477)	$ (2,598)	$ (25,279)	$ 3,239	$ (7,679)	$ (24,638)
Less: Net income allocated to participating restricted stockholders		128			0			0	0
Net income (loss) attributable to common stockholders		$ 5,029			$ (2,598)			$ (7,679)	$ (24,638)
Common shares/units:
Common shares outstanding — basic		33,707			25,073			26,093	25,037
Dilutive effect of potential common shares		0			0			0	0
Common shares outstanding — diluted		33,707			25,073			26,093	25,037
Net earnings per share:
Basic		$ 0.15			$ (0.10)			$ (0.29)	$ (0.98)
Diluted		$ 0.15			$ (0.10)			$ (0.29)	$ (0.98)
Stock Options [Member]
Net earnings per share:
Antidilutive stock options or warrants	[1]	3			116			3	116
Warrants [Member]
Net earnings per share:
Antidilutive stock options or warrants	[2]	9,154			2,174			9,154	2,174

[1] Amount represents options to purchase common stock that are excluded from the diluted net earnings per share calculations because of their antidilutive effect.

[2] Amount represents warrants to purchase common stock that are excluded from the diluted net earnings per share calculations because of their antidilutive effect.