Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2021

Stockholders' Equity Note [Abstract]

Changes in Accumulated Other Comprehensive Loss, Net of Tax

Changes in accumulated other comprehensive loss, net of tax, for the three months ended March 31, 2021 and 2020:

	Three Months Ended March 31, 2021
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges		Defined Benefit Pension and Postretirement Items		Total
Accumulated other comprehensive loss at Jan. 1	$	(23)	$	(1)	$	(24)
Losses reclassified from net accumulated other comprehensive loss:
Interest rate derivatives (net of taxes of $— and $—, respectively) (a)	1		—		1
Net current period other comprehensive income	1		—		1
Accumulated other comprehensive loss at March 31	$	(22)	$	(1)	$	(23)

(a) Included in interest charges

	Three Months Ended March 31, 2020
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges		Defined Benefit Pension and Postretirement Items		Total
Accumulated other comprehensive loss at Jan. 1	$	(24)	$	(3)	$	(27)
Losses reclassified from net accumulated other comprehensive loss:
Interest rate derivatives (net of taxes of $— and $—, respectively) (a)	—		—		—
Net current period other comprehensive income	—		—		—
Accumulated other comprehensive loss at March 31	$	(24)	$	(3)	$	(27)

(a) Included in interest charges