Incentive Plans - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended			1 Months Ended					9 Months Ended	1 Months Ended			9 Months Ended	1 Months Ended
	Sep. 30, 2012	Sep. 30, 2011		Jan. 31, 2012 Performance-Based Restricted Stock Units	Jan. 31, 2012 Performance-Based Restricted Stock Units Minimum	Jan. 31, 2012 Performance-Based Restricted Stock Units Maximum	Aug. 01, 2012 Time Based Restricted Stock Units (RSU)	Feb. 01, 2012 Time Based Restricted Stock Units (RSU) Non Employee Directors, Plan	Sep. 30, 2012 2012 Annual Incentive Plan	Jun. 20, 2012 2012 Annual Incentive Plan Senior Officers	Jun. 20, 2012 2012 Annual Incentive Plan Senior Officers Minimum	Jun. 20, 2012 2012 Annual Incentive Plan Senior Officers Maximum	Sep. 30, 2012 Employee Stock Purchase Plan	Jan. 31, 2012 Annual Incentive Plan, 2007 Annual Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Long term plan expiration year									2022
Maximum number of shares available for issuance									8,700,000				980,000
Maximum number of shares available for issuance, annual rate									1.00%
Shares available for issuance expiration date													Sep. 30, 2017
Granted stock options										227,500				1,643,000
Granted stock options, exercise price										$ 45.70				$ 59.655
Stock-based compensation, fair value assumption model				Monte Carlo valuation model						Black-Scholes valuation model				Black-Scholes valuation model
Granted stock options, valuation per option											$ 12.37	$ 13.10		$ 17.74
Granted restricted stock				653,356			1,996	40,260
Granted restricted stock, fair value					$ 54.90	$ 63.64	$ 54.40	$ 59.33
Granted restricted stock vesting scheme								These shares vest on the third anniversary of the date of grant.
Vested stock options, exercisable period											6 months	3 years
Restricted stock vesting period							Feb. 01, 2015
Proceeds from exercise of stock options and employee stock purchase plans	$ 11,138	$ 8,245	[1]
Income tax benefit realized for the tax deductions from option exercises	$ 3,300	$ 7,400

[1] Reclassified to conform to current presentation.