Retirement Plans - Weighted Average Actuarial Assumptions Used in Calculation of Pension Plans (Detail) (Funded and unfunded pension plans [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Funded and unfunded pension plans [Member]
Weighted average assumptions used to determine benefit obligations at December 31
Discount rate	3.80%	4.60%	3.80%
Rate of compensation increase	5.00%	4.40%	4.30%
Weighted average assumptions used to determine net periodic benefit cost for the years ended December 31
Discount rate	4.60%	4.00%	4.30%
Expected return on plan assets	7.50%	7.50%	7.50%
Rate of compensation increase	4.40%	4.30%	4.30%