Common Stock - Summary of Stock Options (Detail) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Weighted average exercise price, Beginning of year	$ 47.20	$ 38.01	$ 34.19
Stock options granted, weighted average exercise price	$ 84.58	$ 79.68	$ 44.03
Stock options canceled, weighted average exercise price	$ 60.28	$ 40.20	$ 40.53
Stock options exercised, weighted average exercise price	$ 82.26	$ 36.84	$ 30.35
Weighted average exercise price, End of the year	$ 58.69	$ 47.20	$ 38.01
Stock options exercisable, weighted average exercise price	$ 43.99	$ 38.47	$ 36.31
Number of shares under stock option, Beginning of the year	10,481,750	11,039,544	10,255,982
Number of Shares Granted	2,239,088	2,277,946	3,485,283
Number of Shares Cancelled	(228,137)	(241,174)	(232,488)
Number of Shares Exercised	(3,019,219)	(2,594,566)	(2,469,233)
Number of shares under stock option, End of the year	9,473,482	10,481,750	11,039,544
Number of stock options vested and expected to be vest, exercisable	4,823,331	5,073,965	5,067,186

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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