Reconciliation of Statutory U.S. Federal Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory rate	35.00%	35.00%	35.00%
Rate change on deferred taxes	(14.00%)
Transition tax	6.00%
Non-deductible EC charge		25.80%
State	1.80%	2.90%	2.10%
Federal domestic production deduction	(1.10%)	(2.60%)	(1.80%)
Tax on foreign earnings	(4.00%)	(7.40%)	(2.70%)
Other, net	(0.80%)	0.10%	(1.20%)
Effective income tax rate	22.90%	53.80%	31.40%