Other Comprehensive Income

3 Months Ended

Mar. 31, 2019

Stockholders' Equity Note [Abstract]

Other Comprehensive Income

Other Comprehensive Income (Loss)

Changes in accumulated other comprehensive loss, net of tax, for the three months ended March 31, 2019 and 2018:

	Three Months Ended March 31, 2019
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges			Defined Benefit 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	)

	Three Months Ended March 31, 2018
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges			Defined Benefit and Postretirement Items			Total
Accumulated other comprehensive loss at Jan. 1	$	(26.5	)	$	(0.2	)	$	(26.7	)
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	$	(26.2	)	$	(0.2	)	$	(26.4	)

^(a)  Included in interest charges.