Income (Loss) Per Share - Reconciliation of Weighted Average Shares Used in Computation of Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share Disclosure [Line Items]
Net income (loss) attributable to common stockholders	$ 16,265,000	$ 15,682,000	$ (35,435,000)	$ (39,121,000)
Shares used in income (loss) per share - basic (in shares)	27,085	23,106	24,754	23,104
Income (loss) per share - basic (in dollars per share)	$ 0.60	$ 0.68	$ (1.43)	$ (1.69)
Convertible senior notes	$ 14,367,000	$ 1,487,000	$ 0	$ 0
Convertible senior notes (in shares)	31,648	21,426	0	0
Net income (loss) attributable to common stockholders plus assumed exercises and conversion	$ 30,632,000	$ 17,169,000	$ (35,435,000)	$ (39,121,000)
Shares used in income (loss) per share - diluted (in shares)	60,345	45,686	24,754	23,104
Income (loss) per share - diluted (in dollars per share)	$ 0.51	$ 0.38	$ (1.43)	$ (1.69)
Preferred stock dividends	$ 180,000		$ 180,000
Performance stock grants
Earnings Per Share Disclosure [Line Items]
Unvested stock grants	72	832	0	0
Restricted Stock
Earnings Per Share Disclosure [Line Items]
Unvested stock grants	1,540	322	0	0