Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Computed "expected" tax expense, amount	$ 179,530	$ 141,249	$ 108,777
Foreign income tax differential, amount	(24,972)	(16,021)	(11,695)
State taxes net of federal benefits, amount	4,492	4,744	3,858
Foreign-sourced nontaxable income, amount	(8,128)	(11,967)	(8,840)
Other, amount	(6,685)	1,063	2,491
Provision for income taxes, amount	$ 144,236	$ 119,068	$ 94,591
Computed "expected" tax expense, rate	35.00%	35.00%	35.00%
Foreign income tax differential, rate	(4.87%)	(3.97%)	(3.76%)
State taxes net of federal benefits, rate	0.88%	1.18%	1.24%
Foreign-sourced nontaxable income, rate	(1.59%)	(2.97%)	(2.84%)
Other, rate	(1.32%)	0.26%	0.76%
Provision for income taxes, rate	28.10%	29.50%	30.40%