Retirement and Benefit Plans (Plan Assumptions) (Detail)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
For measuring benefit obligations at year end
Discount rate	[1]	3.05%	4.10%	3.47%
For measuring net periodic benefit cost
Discount rate	[1]	4.10%	3.47%	3.97%
Expected return on plan assets	[1]	5.50%	6.00%	6.00%

[1] Since the Plan’s benefits were frozen, except for grandfathered employees, the rate of compensation increase is no longer applicable beginning in 2014 since minimal grandfathered employees are still accruing benefits.