Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified			1 Months Ended
	Aug. 31, 2013	Feb. 28, 2013	Oct. 31, 2013 Subsequent Event Unfavorable Regulatory Action
Commitments and Contingencies [Line Items]
Reserve for environmental legal proceedings	$ 1.1	$ 1.2
Possible penalty for allegedly exceeding power consumption limits during a declared Emergency Curtailment Event			$ 2.4