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Employee Benefit Plans (Assumptions Used For Pension Benefits Accounting) (Details) | 2 Months Ended | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Oct. 31, 2016
Pension Plan [Member] | Qualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Discount rate | 4.10% | 4.30% | 3.60% | 4.10% |
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Discount rate |  | 3.60% | 4.10% | 4.40% |
Expected long-term rate of return on plan assets |  |  |  | 6.75% |
Pension Plan [Member] | Nonqualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Discount rate | 4.10% | 4.30% | 3.60% | 4.10% |
Salary increase | 4.40% |  |  | 4.40% |
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Discount rate |  | 3.60% | 4.10% | 4.40% |
Salary increase |  |  | 4.40% | 4.40% |
Pension Plan [Member] | Minimum [Member] | Qualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Salary increase | 4.00% | 3.50% | 3.50% | 4.00% |
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Discount rate |  |  |  |  |
Salary increase |  | 3.50% | 4.00% | 4.00% |
Expected long-term rate of return on plan assets |  |  | 6.50% | 6.50% |
Pension Plan [Member] | Minimum [Member] | Nonqualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Salary increase |  | 3.50% | 3.50% |  |
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Salary increase |  | 3.50% |  |  |
Pension Plan [Member] | Maximum [Member] | Qualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Salary increase | 4.50% | 4.00% | 4.00% | 4.50% |
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Salary increase |  | 4.00% | 4.50% | 4.40% |
Expected long-term rate of return on plan assets |  | 6.50% | 6.75% |  |
Pension Plan [Member] | Maximum [Member] | Nonqualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Salary increase |  | 4.00% | 4.00% |  |
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Salary increase |  | 4.00% |  |  |
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Discount rate | 4.10% |  |  | 4.10% | 3.80%
Salary increase | 4.50% |  |  | 4.50% | 4.05%
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Discount rate | 3.80% |  |  |  | 4.34%
Salary increase | 4.05% |  |  |  | 4.07%
Expected long-term rate of return on plan assets | 6.75% |  |  |  | 7.25%
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Discount rate | 4.10% |  |  | 4.10% | 3.80%
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Discount rate | 3.80% |  |  |  | 3.85%
Other Post-Retirement Benefit Plans [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Discount rate | 4.10% | 4.30% | 3.60% | 4.10% |
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Discount rate |  | 3.60% | 4.10% | 4.40% |
Expected long-term rate of return on plan assets |  | 6.50% | 6.50% | 6.50% |
Assumed tax rate |  | 35.00% | 35.00% | 35.00% |
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member] |  |  |  |  |
Benefit Obligations [Abstract] |  |  |  |  |
Discount rate | 4.10% |  |  | 4.10% | 3.80%
Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Discount rate | 3.80% |  |  |  | 4.38%
Expected long-term rate of return on plan assets | 6.75% |  |  |  | 7.25%

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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(2) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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