Commitments and Contingencies (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 MMBTU Natual Gas Dollar Equivalent [Member]	Jun. 30, 2013 Pounds Of Flour Dollar Equivalent [Member]	Jun. 30, 2013 Capital Expenditures [Member]	Jul. 10, 2013 Subsequent Event [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 35,165	$ 6,805	$ 9,322
Purchase Commitment, Remaining Minimum Amount Committed				414
Letters of Credit Outstanding, Amount	2,000
Loss Contingency, Range of Possible Loss, Maximum					$ 400