Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Computed "expected" tax expense, amount	$ 57,875	$ 47,794
Foreign income tax differential, amount	(5,860)	(6,073)
State taxes net of federal benefits, amount	2,501	1,597
Foreign-sourced nontaxable income, amount	(2,344)	(4,218)
Domestic production activities deduction, amount	(7,950)
Other, amount	4,365	1,945
Provision for income taxes, amount	$ 48,587	$ 41,045	$ 140,695	$ 113,473
Computed "expected" tax expense, rate	35.00%	35.00%
Foreign income tax differential, rate	(3.50%)	(4.50%)
State taxes net of federal benefits, rate	1.50%	1.20%
Foreign-sourced nontaxable income, rate	(1.40%)	(3.10%)
Domestic production activities deduction, rate	(4.80%)
Other, rate	2.60%	1.50%
Provision for income taxes, rate	29.40%	30.10%