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, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal income tax provision at statutory tax rate		$ 29,384	$ 48,733	$ 39,836
State income tax provision, less applicable federal tax benefit		3,150	1,271	716
Foreign income taxed at different rates		864	(8,075)	(6,325)
U.S. taxation of foreign earnings	[1]	2,348	(1,054)	14
Unrecognized tax benefits		(460)	(47)	23
Domestic production activities deduction			(1,339)	(1,633)
Nontaxable foreign interest income		(1,179)	(2,073)	(2,030)
U.S. tax reform, net impact	[2]	(375)	14,807
Change in accounting methods	[3]	(3,383)	(893)
Stock based compensation, excess tax benefits	[4]	(1,648)	(2,254)	(1,878)
U.S. tax credits		(1,324)	(1,204)	(1,100)
Non-deductible expenses and other items, net	[5]	(204)	(182)	(5)
Total		$ 27,173	$ 47,690	$ 27,618
Percentage of Federal income tax provision at statutory tax rate		21.00%	35.00%	35.00%
Percentage of state income tax provision, less applicable federal tax benefit		2.30%	0.90%	0.60%
Percentage of Foreign income taxed at different rates		0.60%	(5.80%)	(5.60%)
Percentage of U.S. taxation of foreign earnings	[1]	1.70%	(0.80%)
Percentage of Unrecognized tax benefits		(0.30%)
Percentage of Domestic production activities deduction			(1.00%)	(1.40%)
Percentage of Nontaxable foreign interest income		(0.80%)	(1.50%)	(1.80%)
Percentage of U.S. tax reform, net impact	[2]	(0.30%)	10.70%
Percentage of Change in accounting methods	[3]	(2.40%)	(0.60%)
Percentage of stock based compensation, excess tax benefits	[4]	(1.20%)	(1.60%)	(1.70%)
Percentage of U.S. tax credits		(0.90%)	(0.90%)	(1.00%)
Non-deductible expenses and other items, net	[5]	(0.30%)	(0.10%)	0.20%
Percentage of Total income tax provision		19.40%	34.30%	24.30%

[1] Includes cost of global intangible low-taxed income (GILTI) in 2018 and withholding taxes paid on cash repatriated from foreign countries.

[2] Does not include state tax impacts, which are included in state income tax provision, less applicable federal tax benefit.

[3] For 2018, amount represents the federal tax rate change due to certain accounting methods that were adopted on the 2017 federal income tax return. For 2017, amount represents an accounting method change for depreciation.

[4] Excess tax benefits related to employee share-based payment transactions recognized in 2018, 2017 and 2016 resulting from the adoption of ASU No. 2016-9.

[5] Certain 2016 amounts have been reclassified to conform to the 2017 and 2018 presentation.