Schedule of Effective Tax Rate for Income Before Income Taxes (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Effective Tax Rates [Line Items]
Effective tax rates	19.60%	23.20%	54.40%
U.S.
Schedule Of Effective Tax Rates [Line Items]
Effective tax rates	32.30%	36.00%	64.50%
Foreign
Schedule Of Effective Tax Rates [Line Items]
Effective tax rates	9.10%	10.50%	57.70%