Other Comprehensive Income (Loss) (Tables)

6 Months Ended

Jun. 30, 2020

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 and six months ended June 30, 2020 and 2019:

	Three Months Ended June 30, 2020						Three Months Ended June 30, 2019
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges		Defined Benefit Pension and Postretirement Items		Total		Gains and Losses on Cash Flow Hedges		Defined Benefit Pension and Postretirement Items		Total
Accumulated other comprehensive loss at April 1	$	(23.8)	$	(2.5)	$	(26.3)	$	(25.0)	$	(0.2)	$	(25.2)
Losses reclassified from net accumulated other comprehensive loss:
Interest rate derivatives (net of taxes of $0.1, $—, $0.1 and $—, respectively) (a)	0.3		—		0.3		0.3		—		0.3
Net current period other comprehensive income	0.3		—		0.3		0.3		—		0.3
Accumulated other comprehensive loss at June 30	$	(23.5)	$	(2.5)	$	(26.0)	$	(24.7)	$	(0.2)	$	(24.9)