Employee Benefit Plans (Disaggregated Information Related to Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 167,107	$ 182,607	$ 176,751	$ 194,140
Accumulated benefit obligation	167,107	182,607	176,751
Fair value of plan assets	152,820	168,450	157,214	$ 163,270
Funded status of the plan at end of year and accrued benefit (liability) recognized	(14,287)	(14,157)	$ (19,537)
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	152,035	166,191
Accumulated benefit obligation	152,035	166,191
Fair value of plan assets	152,820	168,450
Funded status of the plan at end of year and accrued benefit (liability) recognized	785	2,259
Restoration Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	15,072	16,416
Accumulated benefit obligation	15,072	16,416
Fair value of plan assets	0	0
Funded status of the plan at end of year and accrued benefit (liability) recognized	$ (15,072)	$ (16,416)