Earnings per Share - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock, incremental shares excluded from the computation of diluted EPS	3,329,689	1,823,564	2,220,567
Options to purchase shares of common stock, weighted average exercise price of incremental shares excluded from the computation of diluted EPS	$ 64.72	$ 69.46	$ 58.78