Employee Benefit Plans (Combined Activity in Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Fair value of plan assets at beginning of year	$ 152,820	$ 168,450	$ 157,214
Actual return on plan assets	29,945	(7,739)	23,518
Employer contributions	1,163	1,077	1,049
Benefits paid	(9,755)	(8,968)	(13,331)
Fair value of plan assets at end of year	174,173	152,820	168,450
Benefit obligation at beginning of year	167,107	182,607	176,751
Interest cost	6,472	5,898	6,189
Actuarial (gain) loss	22,817	(12,430)	12,998
Benefits paid	(9,755)	(8,968)	(13,331)
Benefit obligation at end of year	186,641	167,107	182,607
Funded status of the plan at end of year and accrued benefit (liability) recognized	(12,468)	(14,287)	(14,157)
Accumulated benefit obligation at end of year	$ 186,641	$ 167,107	$ 182,607