Income Taxes - Summary of Variations Between the Effective and Statutory U.S. Federal Income Tax Rates (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal income tax provision at statutory tax rate		$ 39,836	$ 36,000	$ 26,437
State tax provision on income less applicable federal tax benefit		716	867	926
Foreign income taxed at different rates		(6,325)	(5,060)	(5,416)
Unrecognized tax benefits		23	1,536	241
Domestic production activities deduction		(1,633)	(884)	(312)
Nontaxable foreign interest income		(2,030)	(2,106)	(2,435)
Stock based compensation, excess tax benefits	[1]	(1,878)
U.S. tax credits		(1,100)	(3,465)	(1,086)
Non-deductible expenses and other items, net	[2]	9	(69)	99
Total		$ 27,618	$ 26,819	$ 18,454
Percentage of Federal income tax provision at statutory tax rate		35.00%	35.00%	35.00%
Percentage of State tax provision on income less applicable federal tax benefit		0.60%	0.80%	1.20%
Percentage of Foreign income taxed at different rates		(5.60%)	(4.90%)	(7.20%)
Percentage of Unrecognized tax benefits		0.00%	1.50%	0.30%
Percentage of Domestic production activities deduction		(1.40%)	(0.90%)	(0.40%)
Percentage of Nontaxable foreign interest income		(1.80%)	(2.00%)	(3.20%)
Percentage of stock based compensation, excess tax benefits	[1]	(1.70%)
Percentage of U.S. tax credits		(1.00%)	(3.40%)	(1.40%)
Percentage of Non-deductible expenses and other items, net	[2]	0.20%	0.00%	0.10%
Percentage of Total income tax provision		24.30%	26.10%	24.40%

[1] Excess tax benefits related to employee share-based payment transactions recognized in 2016 resulting from early adoption of ASU No. 2016-9, as described in Note 1. There is no effect for 2014 and 2015 because the recognition of excess tax benefits in the tax provision is to be done only on a prospective basis, beginning with the year of adopting the new guidance.

[2] Certain 2014 amounts have been reclassified to conform to the current year presentation.