Employee Benefit Plans - Components of Net Periodic Benefit (Income) Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service cost	$ 10,410	$ 8,459	$ 7,746
Interest cost	88,247	96,651	104,485
Expected return on plan assets	(154,006)	(155,432)	(156,832)
Amortization of prior service credit	(147)	(350)	(432)
Amortization of actuarial loss	39,721	38,034	31,641
Net periodic benefit income	$ (15,775)	$ (12,638)	$ (13,392)