Income Taxes - Reconciliation of Effective Tax Rate on Income or Loss and Statutory Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory U.S. tax rate	21.00%	35.00%	35.00%
State income taxes, net of U.S. tax benefit	2.00%	2.60%	3.10%
Federal and State tax credits, net of U.S. tax benefit	(6.00%)	(4.10%)	(5.00%)
Foreign income taxed at other than U.S. statutory rate	1.70%	(0.20%)	1.80%
Effect of foreign rate changes	(0.10%)	0.20%	0.50%
Foreign tax credit	(0.80%)	(1.30%)	(11.30%)
Basis differences of intangibles with an indefinite life	0.00%	0.10%	0.10%
Change in deferred tax valuation allowance	0.50%	(1.90%)	(262.40%)
Accrual for interest and income taxes related to uncertain tax positions	1.80%	2.20%	2.90%
Income (loss) from flowthrough entities	0.60%	1.00%	(0.20%)
Meals and entertainment	0.60%	1.10%	1.50%
Group loss relief	(0.40%)	(0.60%)	(1.60%)
Stock option compensation	(1.10%)	(2.00%)	0.20%
Foreign dividends and earnings inclusion	0.20%	0.70%	9.90%
Foreign tax withholding	0.50%	0.90%	0.60%
Executive compensation limitation	0.70%	0.50%	0.70%
Intra-entity asset transfers	0.80%	(6.30%)	0.00%
Enactment of the Tax Cuts and Jobs Act	0.30%	11.10%	0.00%
Foreign Derived Intangible Income Deduction	(2.70%)	0.00%	0.00%
Other	0.20%	(0.20%)	(2.80%)
Effective tax rate	19.80%	38.80%	(227.00%)