Incentive Plans - Additional Information (Detail)	12 Months Ended							12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)		Dec. 31, 2010 USD ($)		Dec. 31, 2012 Maximum	Feb. 28, 2012 Reduction in Stock Options Exercise Price USD ($)	Dec. 31, 2012 Performance Based Restricted Stock	Dec. 31, 2011 Performance Based Restricted Stock	Dec. 31, 2010 Performance Based Restricted Stock	Dec. 31, 2012 Performance Based Restricted Stock Maximum USD ($)	Dec. 31, 2011 Performance Based Restricted Stock Maximum USD ($)	Dec. 31, 2010 Performance Based Restricted Stock Maximum USD ($)	Dec. 31, 2012 Performance Based Restricted Stock Minimum USD ($)	Dec. 31, 2011 Performance Based Restricted Stock Minimum USD ($)	Dec. 31, 2010 Performance Based Restricted Stock Minimum USD ($)	Dec. 31, 2012 Performance-Based Units USD ($)	Dec. 31, 2011 Performance-Based Units USD ($)	Dec. 31, 2012 Employee Stock Purchase Plan USD ($)	Dec. 31, 2011 Employee Stock Purchase Plan USD ($)	Dec. 31, 2010 Employee Stock Purchase Plan USD ($)	Dec. 31, 2012 Stock Options	Dec. 31, 2012 Time-Lapse Restricted Stock and Restricted Stock Units USD ($)	Dec. 31, 2011 Time-Lapse Restricted Stock and Restricted Stock Units USD ($)	Dec. 31, 2010 Time-Lapse Restricted Stock and Restricted Stock Units USD ($)	Dec. 31, 2012 Phantom Share Units (PSUs) USD ($)	Dec. 31, 2012 Savings Related Share Option Plan (SOP)	Dec. 31, 2012 Savings Related Share Option Plan (SOP) Maximum GBP (£)	Dec. 31, 2012 Savings Related Share Option Plan (SOP) Minimum GBP (£)	Dec. 31, 2012 2012 Annual Incentive Plan	Dec. 31, 2012 2012 Long-Term Plan and the 2007 Long-Term Plan	Dec. 31, 2012 Director Plan	Dec. 31, 2012 SOP plans with holding periods ending in August 2010 Savings Related Share Option Plan (SOP) USD ($)	Dec. 31, 2012 SOP plans with holding periods ending in April 2011 Savings Related Share Option Plan (SOP) USD ($)	Dec. 31, 2012 SOP plans with holding periods ending in May 2012 Savings Related Share Option Plan (SOP) USD ($)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Long term plan expiration year																														2022
Maximum number of shares available for issuance																			980,000											8,700,000
Maximum number of shares available for issuance, annual rate																														1.00%
Number of shares remained available																			302,961											8,472,500
Unvested share-based compensation arrangements, compensation costs to be expensed	$ 56,638,000
Unvested share-based compensation arrangements, number of years compensation costs to be expensed		2 years
Proceeds from exercise of stock options and employee stock purchase plans	12,324,000	15,551,000	[1]	42,995,000	[1]
Income tax benefits realized for the tax deductions from option exercises	5,920,000	8,775,000		15,896,000
Option granted to date, term of years						7 years																									7 years
Employee stock purchase plan, vesting scheme																															Under the 2012 Long-Term Plan and the 2007 Long-Term Plan, one-half of each grant is generally exercisable after two years and the remainder after three years.	Under the Director Plan, one-third of each grant is exercisable after each of the first three years.
Stock-based compensation, fair value assumption model								Monte Carlo valuation model														Black-Scholes pricing model
Total intrinsic value of options exercised	17,197,000	28,145,000		49,929,000
Reduction in stock option exercise price							$ 2.50
Granted restricted stock, valuation											$ 63.64	$ 64.89	$ 50.95	$ 54.90	$ 38.94	$ 42.38							$ 59.33	$ 52.66	$ 52.49
Shares granted								653,355	521,423	449,100																55,000
Compensation expenses																	2,665,000	871,000	272,000	328,000	357,000					305,000
Percentage of targeted amounts paid in cash and awards based on achievement, minimum																	0.00%	0.00%
Percentage of targeted amounts paid in cash and awards based on achievement, maximum																	200.00%	200.00%
Salary that can be withhold by eligible employee for stock purchase																			10.00%
Stock purchase price, percentage of the fair value of the stock																			90.00%								90.00%
Employee Stock purchase plan, termination date																			The ESPP will terminate on the earlier of the date that employees have purchased all 980,000 authorized shares or June 30, 2017.
Employee stock purchases, shares																			24,418	28,555	44,361
Employee stock purchases, per share																			$ 48.54	$ 55.28	$ 51.97
Compensation costs estimation																			Compensation costs related to the ESPP are estimated based on the value of the 10% discount and the fair value of the option that provides for the refund of participant withholdings.								Compensation costs related to the SOP plan are estimated based on the value of the 10% discount and the fair value of the option that allows the employee to receive a repayment of withholdings plus credited interest.
Fair value per share issued under ESPP																			$ 7.30	$ 8.60	$ 7.51
Monthly salary that can be withhold by eligible employee for stock purchase																												250	5
Fair value per share of SOP plans																																	$ 19.90	$ 23.77	$ 22.85
Compensation expense for incentive plans	$ 32,417,000	$ 33,035,000		$ 25,171,000

[1] Reclassified to conform to current presentation.