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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Disclosure [Abstract]
Computed "expected" tax expense, amount	$ 47,794	$ 37,679
Foreign income tax differential, amount	(6,073)	(3,874)
State taxes net of federal benefits, amount	1,597	1,084
Foreign-sourced nontaxable income, amount	(4,218)	(3,360)
Other, amount	1,945	1,228
Effect of statutory rate change, amount		(3,722)
Provision for income taxes, amount	$ 41,045	$ 29,035	$ 113,473	$ 87,111
Computed "expected" tax expense, rate	35.00%	35.00%
Foreign income tax differential, rate	(4.50%)	(3.60%)
State taxes net of federal benefits, rate	1.20%	1.00%
Foreign-sourced nontaxable income, rate	(3.10%)	(3.10%)
Other, rate	1.50%	1.20%
Effect of statutory rate change, rate		(3.50%)
Provision for income taxes, rate	30.10%	27.00%