Employee Benefit Plans (Weighted-Average Assumptions Used to Determine Benefit Obligations) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Benefit obligations, Discount rate	3.68%	4.24%	4.55%
Net periodic benefit cost, Discount rate	4.24%	4.55%	4.20%
Net periodic benefit cost, Expected return on plan assets	7.25%	7.25%	7.25%