Stock-Based Compensation Plans - Additional Information 2 (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended										3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Equity Awards	Sep. 30, 2013 Equity Awards	Sep. 30, 2014 Liability Awards	Sep. 30, 2013 Liability Awards	Sep. 30, 2014 Liability Awards Employees	Sep. 30, 2013 Liability Awards Employees	Sep. 30, 2014 Liability Awards Non Employee Director	Sep. 30, 2013 Liability Awards Non Employee Director	Mar. 31, 2014 Performance Shares	Sep. 30, 2014 Performance Shares		Sep. 30, 2013 Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 13,965	$ 13,244	$ 53,087	$ 40,979	$ 21,000	$ 14,600	$ 19,800	$ 16,000						$ 6,100		$ 0
Units granted					355,000	394,100			208,000	406,300	64,000	18,300		227,929	[1]
Weighted average grant date fair value					$ 84.96	$ 71.13			$ 87.24	$ 75.45	$ 87.97	$ 77.26		$ 86.14	[1]
Vesting period of shares granted to employees					3 years	3 years	3 years	3 years					3 years

[1] Amounts granted reflect the number of performance units granted. The actual payout of shares may be between zero percent and 150% of the performance units granted depending on the total shareholder return ranking compared to the peer companies at the vesting date.