NorthWestern Corporation, doing business as North-Western Energy, provides electricity and natural gas. The Company's segments are Electric operations, Natural gas operations and All other. As of December 31, 2016, the Company provided electricity and natural gas to approximately 709,600 customers in Montana, South Dakota and Nebraska. It generates and distributes electricity in South Dakota; distributes natural gas in South Dakota and Nebraska, and generates and distributes electricity and distributes natural gas in Montana. Its regulated electric utility business in Montana includes generation, transmission and distribution. As of December 31, 2016, it provided retail electricity in 110 communities in South Dakota. Its regulated natural gas utility business in Montana includes production, storage, transmission and distribution. As of December 31, 2016, it provided natural gas to approximately 88,500 customers in 60 South Dakota communities and four Nebraska communities.