Equity Incentive Plans - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
CEO Grant consists of number of vesting tranches	10
Market capitalization	$ 4,000,000,000
Stock-based compensation expense				55,566,000	35,729,000
2012 CEO Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options granted	5,274,901
Initial market capitalization	3,200,000,000
Stock-based compensation expense		$ 3,600,000	$ 400,000	$ 8,800,000	$ 400,000