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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
BASIC:
Net income (loss) attributable to common stockholders	$ 18,091	$ (41,737)	$ 13,710	$ (72,741)
Weighted-average common shares outstanding-basic	867,377	882,408	868,707	875,656
Basic net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
DILUTED:
Weighted-average common shares outstanding-basic	867,377	882,408	868,707	875,656
Weighted-average common shares outstanding-diluted	893,684	882,408	895,207	875,656
Diluted net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
Common Class A [Member]
BASIC:
Net income (loss) attributable to common stockholders	$ 16,240	$ (36,203)	$ 12,223	$ (62,306)
Weighted-average common shares outstanding-basic	778,614	765,403	774,917	750,038
Basic net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
DILUTED:
Net income (loss) attributable to common stockholders-basic	$ 16,240	$ (36,203)	$ 12,223	$ (62,306)
Net income (loss) attributable to common stockholders-diluted	$ 18,091	$ (41,737)	$ 13,702	$ (72,741)
Weighted-average common shares outstanding-basic	778,614	765,403	774,917	750,038
Weighted-average common shares outstanding-diluted	893,684	882,408	895,207	875,656
Diluted net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
Common Class A [Member] | Stock options and employee stock purchase plan [Member]
DILUTED:
Weighted-average effect of dilutive securities	10,125		9,366
Common Class A [Member] | Restricted Stock Units (ZSUs) [Member]
DILUTED:
Weighted-average effect of dilutive securities	15,284		16,236
Common Class A [Member] | Performance Based Restricted Stock Units (ZSUs) [Member]
DILUTED:
Weighted-average effect of dilutive securities	898		898
Common Class B [Member]
BASIC:
Net income (loss) attributable to common stockholders	$ 1,423	$ (4,564)	$ 1,155	$ (8,731)
Weighted-average common shares outstanding-basic	68,246	96,488	73,273	105,101
Basic net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
DILUTED:
Net income (loss) attributable to common stockholders-basic	$ 1,423	$ (4,564)	$ 1,155	$ (8,731)
Net income (loss) attributable to common stockholders-diluted	$ 1,552	$ (4,564)	$ 1,250	$ (8,731)
Weighted-average common shares outstanding-basic	68,246	96,488	73,273	105,101
Weighted-average common shares outstanding-diluted	76,684	96,488	81,646	105,101
Diluted net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
Reallocation of net income (loss) to Class B and Class C shares	$ 129		$ 95
Common Class B [Member] | Stock options and employee stock purchase plan [Member]
DILUTED:
Weighted-average effect of dilutive securities	8,438		8,373
Common Class C [Member]
BASIC:
Net income (loss) attributable to common stockholders	$ 428	$ (970)	$ 324	$ (1,704)
Weighted-average common shares outstanding-basic	20,517	20,517	20,517	20,517
Basic net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
DILUTED:
Net income (loss) attributable to common stockholders-basic	$ 428	$ (970)	$ 324	$ (1,704)
Net income (loss) attributable to common stockholders-diluted	$ 415	$ (970)	$ 314	$ (1,704)
Weighted-average common shares outstanding-basic	20,517	20,517	20,517	20,517
Weighted-average common shares outstanding-diluted	20,517	20,517	20,517	20,517
Diluted net income (loss) per share	$ 0.02	$ (0.05)	$ 0.02	$ (0.08)
Reallocation of net income (loss) to Class B and Class C shares	$ (13)		$ (10)
Class C Convert To Class A [Member] | Common Class A [Member]
DILUTED:
Reallocation of net income (loss) as a result of common stock class conversion	$ 428	$ (970)	$ 324	$ (1,704)
Conversion of common stock class	20,517	20,517	20,517	20,517
Class B convert to Class A [Member] | Common Class A [Member]
DILUTED:
Reallocation of net income (loss) as a result of common stock class conversion	$ 1,423	$ (4,564)	$ 1,155	$ (8,731)
Conversion of common stock class	68,246	96,488	73,273	105,101