Regulatory Assets 1 (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Regulatory Assets Summary [Abstract]
Pension and Other Postretirement Benefits	$ 10,481	$ 18,140
Environmental	35,869	38,384
Missouri Safety Program	448	1,147
Other	10,649	8,545
Regulatory Assets Total	$ 57,447	$ 66,216

The amount of regulatory assets related to environmental remediation.

No definition available.

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- Definition

Regulatory assets not already included in other listed categories.

+ References

No definition available.

+ Details

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- Definition

The amount of regulatory assets related to pension and other postretirement benefits.

+ References

No definition available.

+ Details

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- Details

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- Definition

The amount of regulatory assets related to safety program expenditures.

+ References

No definition available.

+ Details

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- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 9, 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

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