Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2020

Stockholders' Equity Note [Abstract]

Changes in Accumulated Other Comprehensive Loss, Net of Tax

	Three Months Ended March 31, 2019
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges			Defined Benefit Pension and Postretirement Items			Total
Accumulated other comprehensive loss at Jan. 1	$	(25.3	)	$	(0.2	)	$	(25.5	)
Losses reclassified from net accumulated other comprehensive loss:
Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a)	0.3			—			0.3
Net current period other comprehensive income	0.3			—			0.3
Accumulated other comprehensive loss at March 31	$	(25.0	)	$	(0.2	)	$	(25.2	)

^(a) 

Included in interest charges.

Changes in accumulated other comprehensive loss, net of tax, for the three months ended March 31, 2020 and 2019:

	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	$	(24.1	)	$	(2.5	)	$	(26.6	)
Losses reclassified from net accumulated other comprehensive loss:
Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a)	0.3			—			0.3
Net current period other comprehensive income	0.3			—			0.3
Accumulated other comprehensive loss at March 31	$	(23.8	)	$	(2.5	)	$	(26.3	)

^(a) 

Included in interest charges.