SEGMENT INFORMATION (Tables)

9 Months Ended

Sep. 30, 2018

Segment Reporting [Abstract]

Financial information of reportable segments

The following tables show summarized financial information related to our reportable segments for the three and nine months ended September 30, 2018 and 2017:

	Utility Operations
(in millions)	Wisconsin		Illinois		Other States			Total Utility Operations		Electric Transmission		Non-Utility Energy Infrastructure		Corporate and Other			Reconciling Eliminations			WEC Energy Group Consolidated
Three Months Ended
September 30, 2018
External revenues	$	1,388.7	$	197.9	$	50.2		$	1,636.8	$	—	$	4.5	$	2.4		$	—		$	1,643.7
Intersegment revenues	—		—		—			—		—		110.7		—			(110.7		)	—
Other operation and maintenance	525.0		104.5		23.0			652.5		—		3.0		(4.4		)	(98.0		)	553.1
Depreciation and amortization	137.2		43.0		6.4			186.6		—		19.1		7.1			—			212.8
Operating income (loss)	201.4		15.5		(5.4		)	211.5		—		91.6		(0.4		)	—			302.7
Equity in earnings of transmission affiliates	—		—		—			—		33.7		—		—			—			33.7
Interest expense	49.6		12.8		2.1			64.5		—		15.9		32.9			(1.3		)	112.0

	Utility Operations
(in millions)	Wisconsin		Illinois		Other States			Total Utility Operations		Electric Transmission		Non-Utility Energy Infrastructure		Corporate and Other			Reconciling Eliminations			WEC Energy Group Consolidated
Three Months Ended
September 30, 2017
External revenues	$	1,401.3	$	187.2	$	49.8		$	1,638.3	$	—	$	13.6	$	5.6		$	—		$	1,657.5
Intersegment revenues	—		—		—			—		—		111.6		—			(111.6		)	—
Other operation and maintenance *	460.5		99.0		21.5			581.0		—		1.5		(0.4		)	(109.0		)	473.1
Depreciation and amortization	131.5		38.9		6.3			176.7		—		18.2		6.3			—			201.2
Operating income (loss) *	277.5		14.3		(3.0		)	288.8		—		103.4		—			—			392.2
Equity in earnings of transmission affiliates	—		—		—			—		39.2		—		—			—			39.2
Interest expense	48.5		11.0		2.3			61.8		—		16.2		25.4			0.4			103.8

* Includes the retroactive restatement impacts of the implementation of ASU 2017-07. See Note 15, Employee Benefits, for more information on this new standard.

	Utility Operations
(in millions)	Wisconsin		Illinois		Other States		Total Utility Operations		Electric Transmission		Non-Utility Energy Infrastructure		Corporate and Other			Reconciling Eliminations			WEC Energy Group Consolidated
Nine Months Ended
September 30, 2018
External revenues	$	4,303.3	$	973.2	$	292.5	$	5,569.0	$	—	$	26.8	$	6.9		$	—		$	5,602.7
Intersegment revenues	—		—		—		—		—		323.5		—			(323.5		)	—
Other operation and maintenance	1,495.9		320.8		74.5		1,891.2		—		9.2		(2.5		)	(295.2		)	1,602.7
Depreciation and amortization	406.9		125.7		17.5		550.1		—		55.7		22.3			—			628.1
Operating income (loss)	670.2		204.8		38.9		913.9		—		277.0		(12.3		)	—			1,178.6
Equity in earnings of transmission affiliates	—		—		—		—		95.2		—		—			—			95.2
Interest expense	147.5		37.4		6.3		191.2		—		48.0		91.2			(3.2		)	327.2

	Utility Operations
(in millions)	Wisconsin		Illinois		Other States		Total Utility Operations		Electric Transmission		Non-Utility Energy Infrastructure		Corporate and Other			Reconciling Eliminations			WEC Energy Group Consolidated
Nine Months Ended
September 30, 2017
External revenues	$	4,316.6	$	965.7	$	273.4	$	5,555.7	$	—	$	26.1	$	11.7		$	—		$	5,593.5
Intersegment revenues	—		—		—		—		—		333.2		—			(333.2		)	—
Other operation and maintenance *	1,385.9		321.0		73.0		1,779.9		—		4.6		3.5			(330.6		)	1,457.4
Depreciation and amortization	391.1		112.6		18.4		522.1		—		53.1		18.3			—			593.5
Operating income (loss) *	829.6		214.9		35.2		1,079.7		—		299.5		(10.1		)	—			1,369.1
Equity in earnings of transmission affiliates	—		—		—		—		122.9		—		—			—			122.9
Interest expense	145.4		33.0		6.5		184.9		—		46.7		81.3			(2.5		)	310.4

* Includes the retroactive restatement impacts of the implementation of ASU 2017-07. See Note 15, Employee Benefits, for more information on this new standard.