Asset Allocation for the Other Postretirment Benefit Plan and the Target Allocation, by Asset Catergory (Detail) (Other Postretirement Benefit Plans, Defined Benefit)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
Equity Securities
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	20.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	40.00%
Defined Benefit Plan, Actual Plan Asset Allocations	33.00%	30.00%
Debt Securities [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	50.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	70.00%
Defined Benefit Plan, Actual Plan Asset Allocations	62.00%	61.00%
Cash Equivalents [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	5.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	15.00%
Defined Benefit Plan, Actual Plan Asset Allocations	5.00%	9.00%