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, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Current year actuarial loss (gain)	$ 24,613	$ (33,677)	$ 117,867
Recognition of actuarial loss	(39,613)	(31,000)	(39,721)
Current year prior service cost	0	3,327	0
Recognition of prior service (cost) credit	(692)	67	147
Recognition of curtailment gain (loss)	435	(155)	0
Other	0	(50)	0
Total recognized in other comprehensive (loss) income	(15,257)	(61,488)	78,293
Total recognized in net periodic benefit income and other comprehensive (loss) income	$ (33,226)	$ (77,693)	$ 62,518