Other Financial Information (Tables)

12 Months Ended

Dec. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Changes in Operating Working Capital

CHANGES IN WORKING CAPITAL -

(Millions of dollars)	2019			2018			2017
Accounts receivable	$	(33.4	)	$	86.6		$	(41.7	)
Inventories	(6.1		)	(39.0		)	(16.3		)
Prepaid expenses and other current assets	(3.3		)	11.4			(5.2		)
Accounts payable and accrued liabilities	(5.9		)	(56.7		)	26.9
Income taxes payable	—			—			(0.6		)
Net decrease (increase) in noncash operating working capital	$	(48.7	)	$	2.3		$	(36.9	)