Reconciliation of Federal Statutory Tax Rate to Effective Income Tax Rate (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Examination [Line Items]
Statutory U.S. federal income tax rate	21.00%	35.00%	21.00%	35.00%	35.00%
TCJA, impact from change in tax rate	0.00%	0.00%	2.20%	0.00%
Swaps terminated prior to the TCJA	3.50%	0.00%	3.30%	0.00%
TCJA, impact on foreign operations	(3.60%)	0.00%	(1.10%)	0.00%
Effect of foreign operations	3.20%	(2.00%)	3.20%	(1.30%)
Valuation allowance	(0.80%)	0.00%	(1.10%)	0.00%
Provision to return adjustments	0.20%	0.00%	(0.60%)	0.00%
Other, net	(0.50%)	2.50%	0.60%	0.40%
Effective rate	23.00%	35.50%	27.50%	34.10%