Commitments and Contingent Liabilities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Y
Minimum
Loss Contingencies [Line Items]
Time-frame over which the accrued amounts may be paid out, in years	15
Maximum
Loss Contingencies [Line Items]
Time-frame over which the accrued amounts may be paid out, in years	20
Accrued Liabilities
Loss Contingencies [Line Items]
Waste disposed accrued liability	2.0
Other Liabilites
Loss Contingencies [Line Items]
Waste disposed accrued liability	6.7