Employee Benefit Plans (Defined Benefit Pension Plans not Recognized as Component of Combined Net Period Benefit Cost) (Detail) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (57,900)	$ (62,732)
Deferred tax benefit	12,160	21,956
Amounts included in accumulated other comprehensive loss, net of tax	$ (37,718)	$ (40,776)