Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]
Approximate asserted claims plus accrued interest assessed by Louisiana Department of Revenue	$ 30.5
Additional estimated assessments including interest by Louisiana Department of Revenue	3.4
Minimum potential range contingency loss	0
Maximum potential range contingency loss	$ 33.9

Additional estimated assessments including interest by Louisiana Department of Revenue.

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- Definition

Approximate asserted claims plus accrued interest assessed by Louisiana Department of Revenue.

+ References

No definition available.

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- Definition

The estimated maximum amount of possible loss from the contingency.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

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- Definition

The estimated minimum amount of possible loss from the contingency.

+ References

+ Details

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