Income Taxes - Reconciliation of Effective Tax Rate on Income or Loss and Statutory Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory U.S. tax rate	35.00%	35.00%	35.00%
State income taxes, net of U.S. tax benefit	2.60%	3.10%	3.50%
Federal and State tax credits, net of U.S. tax benefit	(4.10%)	(5.00%)	(11.50%)
Foreign income taxed at other than U.S. statutory rate	(0.20%)	1.80%	(2.40%)
Effect of foreign rate changes	0.20%	0.50%	0.90%
Foreign tax credit	(1.30%)	(11.30%)	(12.00%)
Basis differences of intangibles with an indefinite life	0.10%	0.10%	0.10%
Change in deferred tax valuation allowance	(1.90%)	(262.40%)	0.30%
Accrual for interest and income taxes related to uncertain tax positions	2.20%	2.90%	(0.30%)
Income (loss) from flowthrough entities	1.00%	(0.20%)	(2.00%)
Meals and entertainment	1.10%	1.50%	3.40%
Group loss relief	(0.60%)	(1.60%)	(3.70%)
Stock option compensation	(2.00%)	0.20%	(1.90%)
Foreign dividends and earnings inclusion	0.70%	9.90%	7.10%
Foreign tax withholding	0.90%	0.60%	1.40%
Executive compensation limitation	0.50%	0.70%	4.30%
Effective Income Tax Rate Reconciliation, Intra-Entity Asset Transfer, Percent	(6.30%)	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Cuts And Jobs Act Of 2017, Percent	11.10%	0.00%	0.00%
Other	(0.20%)	(2.80%)	5.20%
Effective tax rate	38.80%	(227.00%)	27.40%