Pension and Postretirement Benefits - Net Periodic Benefit Cost or Gain (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Domestic Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 4,433	$ 4,991
Expected return on plan assets	(4,672)	(4,907)
Net periodic benefit cost (gain)	(239)	84
TCN Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		290
Expected return on plan assets	(11)	(345)
Net periodic benefit cost (gain)	$ (11)	$ (55)