Employee Benefit Plans (Company's Benefit Obligations and Funded Status) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in projected benefit obligation:
Service costs	$ 282	$ 519	$ 734
Interest costs	9,116	8,079	13,261
Unfunded Supplemental Benefit Plans
Change in projected benefit obligation:
Benefit obligation at beginning of year	236,773	258,528
Service costs	282	519
Interest costs	9,116	8,079
Actuarial losses (gains)	27,034	(16,517)
Benefits paid	(14,412)	(13,836)
Projected benefit obligation at end of year	258,793	236,773	$ 258,528
Change in plan assets:
Contributions	14,412	13,836
Benefits paid	(14,412)	(13,836)
Fair value of plan assets at end of year	0	0
Reconciliation of funded status, Unfunded status of the plans	258,793	236,773
Amounts recognized in the consolidated balance sheet, Accrued benefit liability	258,793	236,773
Unrecognized net actuarial loss	103,624	80,251
Unrecognized prior service credit	(4,180)	(8,250)
Amounts recognized in accumulated other comprehensive income	99,444	72,001
Accumulated benefit obligation at end of year	$ 258,793	$ 236,773