Employee Benefit Plans (Defined Benefit Pension Plans Recognized as Component of Other Comprehensive Income) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	$ 4,832	$ 9,188	$ 3,118
Deferred tax (expense) benefit	(1,774)	(3,216)	(1,091)
Other comprehensive income (loss), net of tax	$ 3,058	$ 5,972	$ 2,027