Stockholders' Equity - Adjustments for Items Reclassified Out of AOCI (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	$ 1,074	$ 949	$ 3,319	$ 2,788
Employee Benefit Plans [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization relating to employee benefit plans	1,246	1,213	3,843	3,736
Less - related income taxes	172	264	524	948
Total reclassifications, net of tax	$ 1,074	$ 949	$ 3,319	$ 2,788