Stockholders' Equity - Outstanding and Reserved Shares of Common Stock for Future Issuance (Detail)	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Common stock outstanding and reserved shares of common stock for future issuance
Options outstanding	23,399,374		36,115,460	39,601,640
Total reserved shares of common stock for future issuance	47,546,117
2005 Stock Option Plan [Member]
Common stock outstanding and reserved shares of common stock for future issuance
Total reserved shares of common stock for future issuance	0	[1]
2012 Equity Incentive Plan [Member]
Common stock outstanding and reserved shares of common stock for future issuance
Total reserved shares of common stock for future issuance	13,169,316	[1]
2012 Employee Stock Purchase Plan [Member]
Common stock outstanding and reserved shares of common stock for future issuance
Total reserved shares of common stock for future issuance	5,549,918	[1]
Stock Options [Member]
Common stock outstanding and reserved shares of common stock for future issuance
Options outstanding	23,399,374
Restricted Stock Units (RSUs) [Member]
Common stock outstanding and reserved shares of common stock for future issuance
RSUs	5,427,509		1,457,870	0

[1] )Refer to Note 12 for a description of these plan