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Commitments, Guarantees and Contingencies - Transmission (Details) - Great Northern Transmission Line [Member] $ in Millions	Mar. 31, 2016 USD ($) kV Miles
Transmission [Line Items]
Transmission Line Length (Miles) | Miles	220
Transmission Line Capacity (kV) | kV	500
Minimum [Member]
Transmission [Line Items]
Estimated Capital Expenditures	$ 560
Maximum [Member]
Transmission [Line Items]
Estimated Capital Expenditures	$ 710

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- Definition

The estimated amount of certain capital expenditures related to environmental compliance, regulatory matters, or other commitments and/or contingencies. This estimate includes expenditures expected in future periods and expenditures made through the end of the current period.

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- Definition

Capacity of a transmission line in kilovolts.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Length of a transmission line in miles.

+ References

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- Details

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