Note Employee benefits (Postretirement health care benefit plan liabilities) (Detail) - Postretirement Health Care Benefit Plan - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	$ 6,328	$ 6,417
Non current liabilities	$ 156,037	$ 159,582