Employee Benefit Plans - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Current year actuarial loss (gain)	$ 117,867	$ (27,672)	$ 152,415
Recognition of actuarial loss	(39,721)	(38,034)	(31,641)
Current year prior service cost	0	4,768	2,063
Recognition of prior service credit	147	350	432
Total recognized in other comprehensive income (loss)	78,293	(60,588)	123,269
Total recognized in net periodic benefit income and other comprehensive income (loss)	$ 62,518	$ (73,226)	$ 109,877