Stock Transactions (Narrative) (Detail) (USD $)	1 Months Ended	12 Months Ended
	Nov. 26, 2012	Dec. 31, 2012	Dec. 31, 2011	Nov. 29, 2010	Dec. 20, 2010
Class of Stock [Line Items]
Common stock, authorized		475,000,000	475,000,000	130,000,000	475,000,000
Common stock, par value		$ 0.001	$ 0.001	$ 0.001	$ 0.001
Common Stock Split Ratio				2.5
Repurchase of Common Stock	$ 200,000,000	$ 200,000,000	$ 443,000
Stock repurchase date		Nov. 26, 2012
Stock repurchase during period		3,900,000
Stock repurchase during period price per share		$ 51.91