Stockholders' Equity - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013 Director	Feb. 15, 2013	Dec. 31, 2012
Equity [Line Items]
Percentage of directors elected by common stock holders	25.00%
Number of directors	3
Conversion of Class B common stock	1.00
Preferred stock, shares authorized	100,000,000		100,000,000
Preferred stock, par value	$ 0.001		$ 0.001
Preferred stock, shares issued	0		0
Authorized the repurchase of shares of common stock		250,000,000
Common stock outstanding shares repurchased	2,083,709
Aggregate cost of shares repurchased, common stock	$ 142,322,000
Common stock shares remains payable	4,756,000
Remaining authorized share repurchased amount	$ 107,700,000
Dividend declared on common stock	$ 0
Common Stock [Member]
Equity [Line Items]
Common stock, shares authorized	1,600,000,000		1,600,000,000
Common stock, par value	$ 0.001		$ 0.001
Right to voting	one vote per share
Vote per common share	1
Common stock, shares issued	131,372,883		130,060,138
Common stock, shares outstanding	129,289,174		130,060,138
Class B Common Stock [Member]
Equity [Line Items]
Common stock, shares authorized	400,000,000		400,000,000
Common stock, par value	$ 0.001		$ 0.001
Right to voting	10 votes per share
Vote per common share	10
Authorized Class B common stock shares	400,000,000
Common Stock Class B par value per share	$ 0.001
Common stock, shares issued	12,799,999		12,799,999
Common stock, shares outstanding	12,799,999		12,799,999