Weighted Average Assumptions Used to Determine Benefit Obligation (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.00%	4.20%
Health care cost trend, Ultimate
Pension Plans, Defined Benefit | Pre Age Sixty Five
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend, Current
Pension Plans, Defined Benefit | Post Age Sixty Five
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend, Current
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.50%
Rate of compensation increase
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discount rate		3.90%
Rate of compensation increase		3.60%
Health care cost trend, Ultimate	4.90%	5.80%
Other Postretirement Benefit Plans, Defined Benefit | Pre Age Sixty Five
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend, Current	7.80%	7.40%
Other Postretirement Benefit Plans, Defined Benefit | Post Age Sixty Five
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend, Current	7.80%	7.40%