Postretirement Benefit Plans - Asset Allocation Range (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	37.00%	35.00%
Minimum range	30.00%	30.00%
Maximum range	40.00%	40.00%
International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	30.00%	29.00%
Minimum range	20.00%	20.00%
Maximum range	40.00%	40.00%
Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	32.00%	35.00%
Minimum range	25.00%	25.00%
Maximum range	45.00%	45.00%
Cash and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	1.00%	1.00%
Minimum range	0.00%	0.00%
Maximum range	5.00%	5.00%