Stockholders' Equity - Adjustments for Items Reclassified Out of AOCI (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	$ 1,345	$ 1,074	$ 4,855	$ 3,319
Employee Benefit Plans [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization relating to employee benefit plans	1,757	1,246	5,943	3,843
Less - related income taxes	412	172	1,088	524
Total reclassifications, net of tax	$ 1,345	$ 1,074	$ 4,855	$ 3,319