Schedule of Reclassifications from Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Amortization of retirement and postretirement plan items:
Actuarial net loss	$ 3,989	[1]
Prior service cost	234	[1]
Transitional liability	122	[1]
Amortization of retirement and postretirement amount reclassified, Total expense before tax	4,345
Amortization of retirement and postretirement amount reclassified, Tax benefit	1,260
Amortization of retirement and postretirement amount reclassified, Expense net of tax	3,085
Deferred loss on interest rate derivative hedges	741
Deferred loss on interest rate derivative hedges, Tax benefit	255
Deferred loss on interest rate derivative hedges, Net of tax	486
Total reclassifications for period, Net of tax	$ 3,571

[1] These AOCI components are included in the computation of net periodic benefit expense. See Note G for additional information.