Net Income (Loss) Per Share of Common Stock - Schedule of Computation of Basic and Diluted Net Income (Loss) Per Share of Common Stock (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
BASIC AND DILUTED:
Net income (loss) attributable to common stockholders	$ (55,830)	$ (128,828)	$ (911)	$ 5,609	$ (184,658)	$ 4,698
BASIC:
Net income (loss) attributable to common stockholders	$ (55,830)	$ (128,828)	$ (911)	$ 5,609	$ (184,658)	$ 4,698
Weighted-average common shares outstanding – basic	937,334		858,666		931,813	864,117
Net income (loss) per share attributable to common stockholders – basic	$ (0.06)		$ 0.00		$ (0.20)	$ 0.01
DILUTED:
Weighted-average common shares outstanding – basic	937,334		858,666		931,813	864,117
Weighted-average common shares outstanding – diluted	937,334		858,666		931,813	890,285
Net income (loss) per share attributable to common stockholders – diluted	$ (0.06)		$ 0.00		$ (0.20)	$ 0.01
Common Class A [Member]
BASIC AND DILUTED:
Net income (loss) attributable to common stockholders	$ (55,830)		$ (911)		$ (184,658)	$ 4,698
Weighted-average common shares outstanding	937,334				931,813
Net income (loss) per share attributable to common stockholders	$ (0.06)				$ (0.20)
BASIC:
Net income (loss) attributable to common stockholders	$ (55,830)		$ (911)		$ (184,658)	$ 4,698
Weighted-average common shares outstanding – basic			858,666			864,117
Net income (loss) per share attributable to common stockholders – basic			$ 0.00			$ 0.01
DILUTED:
Net income (loss) attributable to common stockholders - basic			$ (911)			$ 4,698
Weighted-average common shares outstanding – basic			858,666			864,117
Weighted-average common shares outstanding – diluted			858,666			890,285
Net income (loss) per share attributable to common stockholders – diluted			$ 0.00			$ 0.01
Common Class A [Member] | Stock Options and Employee Stock Purchase Plan [Member]
DILUTED:
Weighted-average effect of dilutive securities						10,803
Common Class A [Member] | Restricted Stock Units (ZSUs) [Member]
DILUTED:
Weighted-average effect of dilutive securities						14,093
Common Class A [Member] | Performance Based Restricted Stock Units (ZSUs) [Member]
DILUTED:
Weighted-average effect of dilutive securities						1,272