Summary of Stock Option Activity (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock Option Shares
Grants outstanding at beginning of the period	5,273,338	2,694,678	4,190,367	2,522,522
Granted	117,770	1,511,850	1,303,035	1,754,170
Exercised	(26,025)	(55,157)	(74,604)	(119,547)
Canceled or expired	(136,710)	(175,182)	(190,425)	(180,956)
Grants outstanding at end of the period	5,228,373	3,976,189	5,228,373	3,976,189
Grants exercisable at end of the period	1,642,252	714,247	1,642,252	714,247
Weighted Average Exercise Price
Grants outstanding at beginning of the period	$ 24.27	$ 13.35	$ 23.46	$ 11.76
Granted	$ 33.75	$ 34.95	$ 27.45	$ 34.10
Exercised	$ 14.64	$ 7.63	$ 11.87	$ 8.35
Canceled or expired	$ 23.11	$ 9.43	$ 25.13	$ 9.60
Grants outstanding at end of the period	$ 24.56	$ 21.82	$ 24.56	$ 21.82
Grants exercisable at end of the period	$ 17.75	$ 11.81	$ 17.75	$ 11.81