Stockholders' Equity - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 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	2
Conversion of Class B common stock	1
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	675,000
Average price of shares repurchased, common stock	$ 42.4
Common stock shares remains payable	$ 8,292,000
Remaining authorized share repurchased amount	$ 207,600,000
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
Vote per common stock share	One
Common stock, shares issued	131,127,919		130,060,138
Common stock, shares outstanding	130,452,919		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
Vote per common Class B stock 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