Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 8, 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 7

-Footnote 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6676-107765

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3044-108585

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 7, 26

-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.

+ Details

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References+ Details

Investments Investments (Details) (USD $) In Millions, unless otherwise specified					0 Months Ended	3 Months Ended	0 Months Ended		3 Months Ended	0 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	May 29, 2013 Boardwalk Bluegrass [Member] Boardwalk Pipeline Partners, LP [Member]	Jun. 30, 2013 Boardwalk Bluegrass [Member] Boardwalk Pipeline Partners, LP [Member]	May 29, 2013 Boardwalk Bluegrass [Member] Boardwalk Pipelines Holding Company [Member]	May 29, 2013 Boardwalk Moss Lake [Member] Boardwalk Pipeline Partners, LP [Member]	Jun. 30, 2013 Boardwalk Moss Lake [Member] Boardwalk Pipeline Partners, LP [Member]	May 29, 2013 Boardwalk Moss Lake [Member] Boardwalk Pipelines Holding Company [Member]	Jun. 30, 2013 Boardwalk Bluegrass and Boardwalk Moss Lake [Member]	Jun. 30, 2013 Boardwalk Bluegrass and Boardwalk Moss Lake [Member] Boardwalk Pipeline Partners, LP [Member]	Jun. 30, 2013 Boardwalk Bluegrass and Boardwalk Moss Lake [Member] Boardwalk Pipeline Partners, LP [Member]	Jun. 30, 2013 Boardwalk Bluegrass and Boardwalk Moss Lake [Member] Boardwalk Pipelines Holding Company [Member]	Jun. 30, 2013 Boardwalk Bluegrass and Boardwalk Moss Lake [Member] Boardwalk Pipelines Holding Company [Member]	Jun. 30, 2013 Affiliates of Williams [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage											50.00%					50.00%
Variable Interest Entity, Financial or Other Support, Amount												$ 10.0	$ 10.0	$ 100.0	$ 19.7
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					59.00%	26.00%	41.00%	61.00%	61.00%	39.00%
Variable Interest Entity Expected Ownership Percentage														90.00%
Cash and cash equivalents	9.9	3.9	11.4	21.9								4.8	4.8
Investment in unconsolidated affiliates	$ 25.0	$ 0										$ 25.0	$ 25.0