Segments and Related Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Results from Operations by Reportable Segment

(Millions of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
2017
Operating revenues from external customers	$	9,676	$	1,650	$	78		$	—		$	11,404
Intersegment revenues	2		1		—			(3		)	—
Total revenues	$	9,678	$	1,651	$	78		$	(3	)	$	11,404
Depreciation and amortization	$	1,298	$	174	$	7		$	—		$	1,479
Interest charges and financing costs	449		57		122			—			628
Income tax expense (benefit)	528		23		(9		)	—			542
Net income (loss)	1,066		182		(100		)	—			1,148

(Millions of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
2016
Operating revenues from external customers	$	9,500	$	1,531	$	76		$	—		$	11,107
Intersegment revenues	1		1		—			(2		)	—
Total revenues	$	9,501	$	1,532	$	76		$	(2	)	$	11,107
Depreciation and amortization	$	1,136	$	160	$	7		$	—		$	1,303
Interest charges and financing costs	450		54		116			—			620
Income tax expense (benefit)	567		76		(62		)	—			581
Net income (loss)	1,067		124		(68		)	—			1,123

(Millions of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
2015
Operating revenues from external customers	$	9,276	$	1,672	$	76		$	—		$	11,024
Intersegment revenues	2		1		—			(3		)	—
Total revenues	$	9,278	$	1,673	$	76		$	(3	)	$	11,024
Depreciation and amortization	$	963	$	155	$	6		$	—		$	1,124
Interest charges and financing costs	426		50		93			—			569
Income tax expense (benefit)	509		60		(26		)	—			543
Net income (loss)	921		106		(43		)	—			984