Employee Benefit Plans (Disaggregated Information Related to Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 186,641	$ 167,107	$ 182,607	$ 176,751
Accumulated benefit obligation	186,641	167,107	182,607
Fair value of plan assets	174,173	152,820	168,450	$ 157,214
Funded status of the plan at end of year and accrued benefit (liability) recognized	(12,468)	(14,287)	$ (14,157)
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	170,541	152,035
Accumulated benefit obligation	170,541	152,035
Fair value of plan assets	174,173	152,820
Funded status of the plan at end of year and accrued benefit (liability) recognized	3,632	785
Restoration Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	16,100	15,072
Accumulated benefit obligation	16,100	15,072
Fair value of plan assets	0	0
Funded status of the plan at end of year and accrued benefit (liability) recognized	$ (16,100)	$ (15,072)