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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
BASIC:
Net income (loss) attributable to common stockholders	$ 5,093	$ (4,446)	$ (4,381)	$ (31,004)
Weighted-average common shares outstanding-basic	863,125	873,393	869,025	872,243
Basic net income (loss) per share	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
DILUTED:
Weighted-average common shares outstanding-basic	863,125	873,393	869,025	872,243
Weighted-average common shares outstanding-diluted	887,991	873,393	869,025	872,243
Diluted net income (loss) per share	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
Common Class A [Member]
BASIC:
Net income (loss) attributable to common stockholders	$ 4,565	$ (3,805)	$ (3,896)	$ (26,384)
Weighted-average common shares outstanding-basic	773,704	747,482	772,679	742,271
Basic net income (loss) per share	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
DILUTED:
Net income (loss) attributable to common stockholders-basic	$ 4,565	$ (3,805)	$ (3,896)	$ (26,384)
Net income (loss) attributable to common stockholders-diluted	$ 5,093	$ (4,446)	$ (4,381)	$ (31,004)
Weighted-average common shares outstanding-basic	773,704	747,482	772,679	742,271
Weighted-average common shares outstanding-diluted	887,991	873,393	869,025	872,243
Diluted net income (loss) per share	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
Common Class A [Member] | Stock options and employee stock purchase plan [Member]
DILUTED:
Weighted-average effect of dilutive securities	9,811
Common Class A [Member] | Restricted Stock Units (ZSUs) [Member]
DILUTED:
Weighted-average effect of dilutive securities	14,710
Common Class A [Member] | Performance Based Restricted Stock Units (ZSUs) [Member]
DILUTED:
Weighted-average effect of dilutive securities	345
Common Class B [Member]
BASIC:
Net income (loss) attributable to common stockholders	$ 407	$ (537)	$ (382)	$ (3,891)
Weighted-average common shares outstanding-basic	68,904	105,394	75,829	109,455
Basic net income (loss) per share	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
DILUTED:
Net income (loss) attributable to common stockholders-basic	$ 407	$ (537)	$ (382)	$ (3,891)
Net income (loss) attributable to common stockholders-diluted	$ 407	$ (537)	$ (382)	$ (3,891)
Weighted-average common shares outstanding-basic	68,904	105,394	75,829	109,455
Weighted-average common shares outstanding-diluted	69,821	105,394	75,829	109,455
Diluted net income (loss) per share	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
Common Class B [Member] | Stock options and employee stock purchase plan [Member]
DILUTED:
Weighted-average effect of dilutive securities	917
Common Class C [Member]
BASIC:
Net income (loss) attributable to common stockholders	$ 121	$ (104)	$ (103)	$ (729)
Weighted-average common shares outstanding-basic	20,517	20,517	20,517	20,517
Basic net income (loss) per share	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
DILUTED:
Net income (loss) attributable to common stockholders-basic	$ 121	$ (104)	$ (103)	$ (729)
Net income (loss) attributable to common stockholders-diluted	$ 121	$ (104)	$ (103)	$ (729)
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	$ 0.01	$ (0.01)	$ (0.01)	$ (0.04)
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	$ 121	$ (104)	$ (103)	$ (729)
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	$ 407	$ (537)	$ (382)	$ (3,891)
Conversion of common stock class	68,904	105,394	75,829	109,455