Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Tax Disclosure [Abstract]
Income tax expense at federal statutory rate, amount	$ 37,679	$ 28,909
Foreign income tax differential, amount	(3,874)	(3,030)
State taxes, net of federal benefit, amount	1,084	1,366
Foreign-sourced nontaxable income, amount	(3,360)	(1,826)
Other, amount	1,228	997
Effect of Statutory Rate Change , amount	(3,722)	(3,473)
Provision for income taxes, amount	$ 29,035	$ 22,943	$ 87,111	$ 65,483
Income tax expense at federal statutory rate, rate	35.00%	35.00%
Foreign income tax differential, rate	(3.60%)	(3.60%)
State taxes, net of federal benefit, rate	1.00%	1.70%
Foreign-sourced nontaxable income, rate	(3.10%)	(2.20%)
Other, rate	1.20%	1.00%
Effect of Statutory Rate Change , rate	(3.50%)	(4.10%)
Provision for income taxes, rate	26.90%	27.80%