Employee Benefit Plans (The Weighted-Average Discount Rate Assumptions Used to Determine Net Periodic Benefit Costs) (Detail) - Unfunded Supplemental Benefit Plans	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate for projected benefit obligation	4.32%	3.61%	4.03%
Discount rate for service cost	4.55%	3.78%	4.32%
Discount rate for interest cost	4.00%	3.23%	3.43%