Financing Activities (Notes)	6 Months Ended
Jun. 30, 2019
Financing Activities [Abstract]
Long-term Debt [Text Block]	Financing Activities In June 2019, we priced $150 million aggregate principal amount of Montana First Mortgage Bonds, at a fixed interest rate of 3.98% maturing in 2049, and issued $50 million of these bonds in a transaction exempt from the registration requirements of the Securities Act of 1933, as amended. Proceeds were used to repay a portion of our outstanding borrowings under our revolving credit facilities and for other general corporate purposes. The bonds are secured by our electric and natural gas assets in Montana. We expect to issue the remaining $100 million of these bonds in September 2019.

Financing Activities (Notes)

6 Months Ended

Jun. 30, 2019

Financing Activities

In June 2019, we priced $150 million aggregate principal amount of Montana First Mortgage Bonds, at a fixed interest rate of 3.98% maturing in 2049, and issued $50 million of these bonds in a transaction exempt from the registration requirements of the Securities Act of 1933, as amended. Proceeds were used to repay a portion of our outstanding borrowings under our revolving credit facilities and for other general corporate purposes. The bonds are secured by our electric and natural gas assets in Montana. We expect to issue the remaining $100 million of these bonds in September 2019.