Employee Benefit Plans - Components of Net Periodic Benefit Income for the Pension Plans (Detail) - Pension Benefits [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,106	$ 2,293	$ 6,257	$ 7,083
Interest cost	26,195	24,503	78,505	73,746
Expected return on plan assets	(39,296)	(37,487)	(117,767)	(112,809)
Amortization of prior service credit	(108)	(141)	(324)	(423)
Amortization of actuarial loss	7,860	9,528	23,530	28,769
Net periodic benefit income	$ (3,243)	$ (1,304)	$ (9,799)	$ (3,634)