Summarizes Stock Option Activity (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Stock Options, Outstanding at December 31, 2011, in shares	24,559
Number of Stock Options, Granted, in shares	3,401
Number of Stock Options, Exercised, in shares	(6,743)
Number of Stock Options, Forfeited/expired, in shares	(592)
Number of Stock Options, Outstanding at December 31, 2012, in shares	20,625
Number of Stock Options, Vested and expected-to-vest at December 31, 2012, in shares	20,517
Number of Stock Options, Vested at December 31, 2012, in shares	14,873
Weighted Average Exercise Price, Outstanding at December 31, 2011, in dollars per share	$ 78.45
Weighted Average Exercise Price, Granted, in dollars per share	$ 82.01
Weighted Average Exercise Price, Exercised, in dollars per share	$ 65.22
Weighted Average Exercise Price, Forfeited/expired, in dollars per share	$ 85.85
Weighted Average Exercise Price, Outstanding at December 31, 2012, in dollars per share	$ 83.15
Weighted Average Exercise Price, Vested and expected-to-vest at December 31, 2012, in dollars per share	$ 83.16
Weighted Average Exercise Price, Vested at December 31, 2012, in dollars per share	$ 84.35
Weighted Average Remaining Contractual Life, Outstanding at December 31, 2012, in years	5 years 8 months
Weighted Average Remaining Contractual Life, Vested and expected-to-vest at December 31, 2012, in years	5 years 8 months
Weighted Average Remaining Contractual Life, Vested at December 31, 2012, in years	4 years 8 months
Aggregate Intrinsic Value, Outstanding at December 31, 2012	$ 248.9
Aggregate Intrinsic Value, Vested and expected-to-vest at December 31, 2012	247.8
Aggregate Intrinsic Value, Vested at December 31, 2012	$ 178.4