Asset Retirement Obligations (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 273,987,000us-gaap_AssetRetirementObligation	$ 296,870,000us-gaap_AssetRetirementObligation
Accretion	17,962,000	31,461,000
New obligations	1,346,000	2,225,000
Changes in estimates of existing obligations (1)	23,031,000	(27,628,000)
Property dispositions/obligations settled	(19,851,000)	(28,941,000)
Ending balance	296,475,000us-gaap_AssetRetirementObligation	273,987,000us-gaap_AssetRetirementObligation
Annual funding obligation	36,400,000
Asset retirement obligations, net [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Changes in estimates of existing obligations (1)		(28,000,000)
Asset retirement obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Changes in estimates of existing obligations (1)	23,000,000	(36,000,000)
Eminence natural gas storage caverns [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Changes in estimates of existing obligations (1)		9,000,000
External ARO trust [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Annual funding obligation	$ 36,400,000

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Asset Retirement Obligation

-URI http://asc.fasb.org/extlink&oid=6505190

+ Details

Name:	us-gaap_AssetRetirementObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

+ Details

Name:	us-gaap_AssetRetirementObligationAccretionExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of asset retirement obligations incurred during the period.

+ References

+ Details

Name:	us-gaap_AssetRetirementObligationLiabilitiesIncurred
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

+ References

+ Details

Name:	us-gaap_AssetRetirementObligationLiabilitiesSettled
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the Increase or Decrease in the amount of the asset retirement obligation during the current period for changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

+ Details

Name:	us-gaap_AssetRetirementObligationRevisionOfEstimate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum amount of other commitment maturing in the next fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherCommitmentDueInNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_UnusualOrInfrequentItemAxis=tgpl_AssetretirementobligationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnusualOrInfrequentItemAxis=tgpl_AssetretirementobligationsnetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnusualOrInfrequentItemAxis=tgpl_EminencenaturalgasstoragecavernsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnusualOrInfrequentItemAxis=tgpl_ExternaltrustMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: