Commitments - Additional Information (Detail)	Jun. 30, 2012 cf
Commitments and Contingencies Disclosure [Line Items]
Natural gas deliveries contract, cubic feet per day	50,000,000
Natural gas deliveries contract, average price per thousand cubic feet, in Canadian dollars	4.43

The delivery price committed to in the contract.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 8

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