SEGMENT INFORMATION

We use operating income to measure segment profitability and to allocate resources to our businesses. At December 31, 2017, we reported two segments, which are described below.

Our utility segment includes our electric and natural gas utility operations. Our electric utility operations are engaged in the generation, distribution, and sale of electricity in northeastern Wisconsin. Our natural gas utility operations are engaged in the purchase, distribution, and sale of natural gas to retail customers and the transportation of customer-owned natural gas in northeastern Wisconsin. Effective January 1, 2017, we transferred our customers and electric and natural gas distribution assets located in the Upper Peninsula of Michigan to UMERC. See Note 3, Related Parties for more information.

During 2017, the other segment included non-utility activities, as well as equity earnings from our investment in WRPC. During 2016 and 2015, the other segment included non-utility activities as well as equity earnings from our investments in WRPC and WPSI, which holds an approximate 34% interest in ATC, a for-profit, electric transmission company regulated by the FERC and certain state regulatory commissions. Effective January 1, 2017, we transferred our 10.37% ownership interest in WPSI to another subsidiary of Integrys. See Note 3, Related Parties, for more information.

All of our operations and assets are located within the United States. The following tables show summarized financial information related to our reportable segments for the years ended December 31, 2017, 2016, and 2015.



2017 (in millions)	Utility		Other			Reconciling Eliminations		Wisconsin Public Service Corporation Consolidated
External revenues	$	1,485.4	$	—		$	—	$	1,485.4
Other operation and maintenance	434.3		1.5			—		435.8
Depreciation and amortization	139.3		—			—		139.3
Operating income (loss)	298.5		(1.6		)	—		296.9
Other income, net	9.2		2.7			—		11.9
Interest expense	54.2		—			—		54.2
Capital expenditures	335.8		—			—		335.8
Total assets	4,678.1		70.6			—		4,748.7



2016 (in millions)	Utility		Other			Reconciling Eliminations			Wisconsin Public Service Corporation Consolidated
External revenues	$	1,448.2	$	—		$	—		$	1,448.2
Intersegment revenues	—		0.3			(0.3		)	—
Other operation and maintenance	492.5		1.0			(0.3		)	493.2
Depreciation and amortization	124.0		0.1			—			124.1
Operating income (loss)	264.4		(0.9		)	—			263.5
Other income, net	23.3		7.5			—			30.8
Interest expense	48.0		0.1			—			48.1
Capital expenditures	311.1		—			—			311.1
Total assets	4,686.4		121.8			—			4,808.2



2015 (in millions)	Utility		Other		Reconciling Eliminations			Wisconsin Public Service Corporation Consolidated
External revenues	$	1,483.3	$	—	$	—		$	1,483.3
Intersegment revenues	—		0.8		(0.8		)	—
Other operation and maintenance	493.9		0.3		(0.8		)	493.4
Depreciation and amortization	120.7		0.3		—			121.0
Operating income	228.0		0.1		—			228.1
Other income, net	16.0		9.6		—			25.6
Interest expense	53.2		0.3		—			53.5
Capital expenditures	371.0		—		—			371.0
Total assets	4,416.8		88.3		—			4,505.1