Stockholders' Equity - Adjustments for Items Reclassified Out of AOCI (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	$ 10,735	$ 7,951	$ 2,526
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization relating to employee benefit plans	13,070	10,171	4,283
Less - related income taxes	2,335	2,220	1,757
Total reclassifications, net of tax	$ 10,735	$ 7,951	$ 2,526