Selected Quarterly Financial Data - (unaudited) (Restated) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue:
Consumer revenue	$ 94,068	$ 88,386	$ 82,574	$ 75,094	$ 70,775	$ 65,579	$ 61,616	$ 56,708	$ 340,121	$ 254,678	$ 193,949
Enterprise revenue	8,237	7,353	6,946	7,001	8,041	6,538	6,267	904	29,537	21,750
Total revenue	102,305	95,739	89,520	82,095	78,816	72,117	67,883	57,612	369,658	276,428	193,949
Gross profit	76,110	70,852	64,326	58,305	56,627	52,355	48,758	38,772	269,593	196,512	131,319
Income (loss) from operations	15,293	6,736	(1,404)	(3,444)	5,700	6,223	1,379	(209)	17,181	13,093	4,843
Net income (loss)	$ 52,976	$ 6,466	$ (1,445)	$ (3,542)	$ 4,080	$ 7,868	$ (6,898)	$ 18,453	$ 54,455	$ 23,503	$ (4,257)
Basic	$ 0.58	$ 0.07	$ (0.02)	$ (0.04)	$ 0.01	$ 0.06	$ (0.56)	$ 0.34	$ 0.61	$ 0.18	$ (1.24)
Diluted	$ 0.54	$ 0.07	$ (0.02)	$ (0.04)	$ 0.01	$ (0.16)	$ (0.59)	$ 0.22	$ 0.57	$ 0.09	$ (1.24)