Employee Benefit Plans (Notes)	12 Months Ended
Dec. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans [Text Block]	BENEFIT PLANS Certain of the benefit costs charged to us by Williams associated with employees who directly support us are described below. Additionally, allocated corporate expenses from Williams to us also include amounts related to these same employee benefits, which are not included in the amounts presented below. Pension and Other Postretirement Benefit Plans Williams has noncontributory defined benefit pension plans (Williams Pension Plan, Williams Inactive Employees Pension Plan and The Williams Companies Retirement Restoration Plan) that provide pension benefits for its eligible employees. Pension costs charged to us by Williams was $12.8 million, $15.6 million and $8.7 million for 2018, 2017, and 2016, respectively. Included in our pension costs are settlement charges of $2.7 million and $7.6 million for 2018 and 2017, respectively. These amounts reflect the portion of Williams’ settlement charge directly charged to us which was required as a result of lump-sum benefit payments made under Williams’ program to pay out certain deferred vested pension benefits, as well as lump-sum benefit payments made throughout 2018 and 2017. In addition, we were charged $2.7 million and $4.6 million for 2018 and 2017, respectively, of allocated corporate expenses also associated with the settlement charge. Williams makes annual cash contributions to the pension plans, based on annual actuarial estimates, which Transco recovers through rates that are set through periodic general rate filings. Effective with the RP12-993 Settlement, any amounts of annual contributions that exceed an upper threshold or fall below a lower threshold are recorded as adjustments to income and collected or refunded through future rate adjustments. The amount of deferred pension collections recorded as a regulatory liability at December 31, 2018 and 2017 were $48.5 million and $32.5 million, respectively. Williams provides subsidized retiree health care and life insurance benefits to certain eligible participants. Generally, participants that were employed by Williams on or before December 31, 1991 or December 31, 1995, if they were employees or retirees of Transco Energy Company and its subsidiaries, are eligible for subsidized retiree health care benefits. We recognized other postretirement benefit income of $5.9 million, $10.9 million and $12.0 million for 2018, 2017, and 2016, respectively. We have been allowed by rate case settlements to collect or refund in future rates any differences between the actuarially determined costs and amounts currently being recovered in rates related to other postretirement benefits. Any differences between the annual actuarially determined cost and amounts currently being recovered in rates are recorded as an adjustment to expense and collected or refunded through future rate adjustments. The amount of other postretirement benefits costs deferred as a regulatory liability at December 31, 2018 and 2017 are $79.8 million and $73.9 million, respectively. These amounts are comprised of amounts being deferred for future rate treatment of $73.9 million and $65.4 million at December 31, 2018 and 2017, respectively, and amounts of $5.9 million and $8.5 million being amortized over a period of approximately 8 years per Docket No. RP12-993 at December 31, 2018 and 2017, respectively. Defined Contribution Plan Williams maintains a defined contribution plan for substantially all of its employees. Williams charged us compensation expense of $7.9 million, $7.7 million and $6.5 million in 2018, 2017 and 2016, respectively, for Williams’ company matching contributions to this plan. Employee Stock-Based Compensation Plan Information The Williams Companies, Inc. 2007 Incentive Plan, as subsequently amended and restated, (Plan) provides for Williams’ common stock based awards to both employees and non-management directors. The Plan permits the granting of various types of awards including, but not limited to, restricted stock units and stock options. Awards may be granted for no consideration other than prior and future services or based on certain financial performance targets achieved. Williams currently bills us directly for compensation expense related to stock-based compensation awards based on the fair value of the awards. We are also billed for our proportionate share of Williams’ and other affiliates’ stock-based compensation expense through various allocation processes. Total stock-based compensation expense for the years ended December 31, 2018, 2017, and 2016 was $6.3 million, $5.7 million and $4.0 million, respectively, excluding amounts allocated from WPZ and Williams.

BENEFIT PLANS

Certain of the benefit costs charged to us by Williams associated with employees who directly support us are described below. Additionally, allocated corporate expenses from Williams to us also include amounts related to these same employee benefits, which are not included in the amounts presented below.

Pension and Other Postretirement Benefit Plans

Williams has noncontributory defined benefit pension plans (Williams Pension Plan, Williams Inactive Employees Pension Plan and The Williams Companies Retirement Restoration Plan) that provide pension benefits for its eligible employees. Pension costs charged to us by Williams was $12.8 million, $15.6 million and $8.7 million for 2018, 2017, and 2016, respectively. Included in our pension costs are settlement charges of $2.7 million and $7.6 million for 2018 and 2017, respectively. These amounts reflect the portion of Williams’ settlement charge directly charged to us which was required as a result of lump-sum benefit payments made under Williams’ program to pay out certain deferred vested pension benefits, as well as lump-sum benefit payments made throughout 2018 and 2017. In addition, we were charged $2.7 million and $4.6 million for 2018 and 2017, respectively, of allocated corporate expenses also associated with the settlement charge.

Williams makes annual cash contributions to the pension plans, based on annual actuarial estimates, which Transco recovers through rates that are set through periodic general rate filings. Effective with the RP12-993 Settlement, any amounts of annual contributions that exceed an upper threshold or fall below a lower threshold are recorded as adjustments to income and collected or refunded through future rate adjustments. The amount of deferred pension collections recorded as a regulatory liability at December 31, 2018 and 2017 were $48.5 million and $32.5 million, respectively.

Williams provides subsidized retiree health care and life insurance benefits to certain eligible participants. Generally, participants that were employed by Williams on or before December 31, 1991 or December 31, 1995, if they were employees or retirees of Transco Energy Company and its subsidiaries, are eligible for subsidized retiree health care benefits. We recognized other postretirement benefit income of $5.9 million, $10.9 million and $12.0 million for 2018, 2017, and 2016, respectively.

We have been allowed by rate case settlements to collect or refund in future rates any differences between the actuarially determined costs and amounts currently being recovered in rates related to other postretirement benefits. Any differences between the annual actuarially determined cost and amounts currently being recovered in rates are recorded as an adjustment to expense and collected or refunded through future rate adjustments. The amount of other postretirement benefits costs deferred as a regulatory liability at December 31, 2018 and 2017 are $79.8 million and $73.9 million, respectively. These amounts are comprised of amounts being deferred for future rate treatment of $73.9 million and $65.4 million at December 31, 2018 and 2017, respectively, and amounts of $5.9 million and $8.5 million being amortized over a period of approximately 8 years per Docket No. RP12-993 at December 31, 2018 and 2017, respectively.

Defined Contribution Plan

Williams maintains a defined contribution plan for substantially all of its employees. Williams charged us compensation expense of $7.9 million, $7.7 million and $6.5 million in 2018, 2017 and 2016, respectively, for Williams’ company matching contributions to this plan.

Employee Stock-Based Compensation Plan Information

The Williams Companies, Inc. 2007 Incentive Plan, as subsequently amended and restated, (Plan) provides for Williams’ common stock based awards to both employees and non-management directors. The Plan permits the granting of various types of awards including, but not limited to, restricted stock units and stock options. Awards may be granted for no consideration other than prior and future services or based on certain financial performance targets achieved.

Williams currently bills us directly for compensation expense related to stock-based compensation awards based on the fair value of the awards. We are also billed for our proportionate share of Williams’ and other affiliates’ stock-based compensation expense through various allocation processes.

Total stock-based compensation expense for the years ended December 31, 2018, 2017, and 2016 was $6.3 million, $5.7 million and $4.0 million, respectively, excluding amounts allocated from WPZ and Williams.