Pension and Other Postretirement Benefits - Summary of Plan Asset Allocations (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Target Plan Asset Allocation, Other	66.00%
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets, Equity	31.00%	30.00%
Plan Assets, Fixed Income	62.00%	62.00%
Plan Assets, Other	7.00%	8.00%
Plan Assets, Total	100.00%	100.00%
Target Plan Asset Allocation, Equity	28.00%	32.00%
Target Plan Asset Allocation, Fixed Income	66.00%	62.00%
Target Plan Asset Allocation, Other	6.00%	6.00%
Target Plan Asset Allocation, Total	100.00%	100.00%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets, Equity	63.00%	62.00%
Plan Assets, Fixed Income	31.00%	36.00%
Plan Assets, Other	6.00%	2.00%
Plan Assets, Total	100.00%	100.00%
Target Plan Asset Allocation, Equity	60.00%	60.00%
Target Plan Asset Allocation, Fixed Income	35.00%	35.00%
Target Plan Asset Allocation, Cash	5.00%	5.00%
Target Plan Asset Allocation, Total	100.00%	100.00%