Asset Allocation Ranges and Actual Allocation, USRIP (Detail) (U.S. Retirement Income Plan, or USRIP)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Large-Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Range minimum	10.00%
Range maximum	35.00%
Actual	13.90%	16.60%
Small- and Mid-Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Range minimum	0.00%
Range maximum	15.00%
Actual	1.30%	5.20%
International Equity
Defined Benefit Plan Disclosure [Line Items]
Range minimum	10.00%
Range maximum	30.00%
Actual	10.70%	13.70%
Private Equity
Defined Benefit Plan Disclosure [Line Items]
Range minimum	2.00%
Range maximum	10.00%
Actual	6.20%	6.10%
Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Range minimum	10.00%
Range maximum	30.00%
Actual	17.30%	18.00%
Real Assets
Defined Benefit Plan Disclosure [Line Items]
Range minimum	2.00%
Range maximum	10.00%
Actual	5.20%	6.30%
Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Range minimum	15.00%
Range maximum	40.00%
Actual	34.80%	33.10%
Cash
Defined Benefit Plan Disclosure [Line Items]
Range minimum	0.00%
Range maximum	15.00%
Actual	10.60%	1.00%