Other Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2018

Stockholders' Equity Note [Abstract]

Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax

Changes in accumulated other comprehensive loss, net of tax, for the year ended Dec. 31:

	2018
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges				Defined Benefit Pension and Postretirement Items				Total
Accumulated other comprehensive loss at Jan. 1	$	(0.8	)		$	(0.7	)		$	(1.5	)
Losses reclassified from net accumulated other comprehensive loss:
Interest rate derivatives (net of taxes of $0 and $0, respectively)	0.1			(a)	—				0.1
Amortization of net actuarial loss (net of taxes of $0 and $0, respectively)	—				—			(b)	—
Net current period other comprehensive income	0.1				—				0.1
Accumulated other comprehensive loss at Dec. 31	$	(0.7	)		$	(0.7	)		$	(1.4	)

	2017
(Millions of Dollars)	Gains and Losses on Cash Flow Hedges				Defined Benefit Pension and Postretirement Items				Total
Accumulated other comprehensive loss at Jan. 1	$	(0.7	)		$	(0.6	)		$	(1.3	)
Losses reclassified from net accumulated other comprehensive loss:
Interest rate derivatives (net of taxes of $0.1 and $0, respectively)	—			(a)	—				—
Amortization of net actuarial loss (net of taxes of $0 and $0, respectively)	—				0.1			(b)	0.1
Net current period other comprehensive income (loss)	—				0.1				0.1
Adoption of ASU No. 2018-02 (c)	(0.1		)		(0.2		)		(0.3		)
Accumulated other comprehensive loss at Dec. 31	$	(0.8	)		$	(0.7	)		$	(1.5	)