Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Computed "expected" tax expense, amount	$ 48,877	$ 38,056
Foreign income tax differential, amount	(4,495)	(4,408)
State taxes net of federal benefits, amount	1,994	1,219
Foreign-sourced nontaxable income, amount	(2,882)	(3,138)
Other, amount	2,001	1,293
Provision for income taxes, amount	$ 45,495	$ 33,022
Computed "expected" tax expense, rate	35.00%	35.00%
Foreign income tax differential, rate	(3.20%)	(4.00%)
State taxes net of federal benefits, rate	1.40%	1.10%
Foreign-sourced nontaxable income, rate	(2.00%)	(2.90%)
Other, rate	1.40%	1.30%
Provision for income taxes, rate	32.60%	30.50%