Supplemental Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2020

Supplemental Cash Flow Elements [Abstract]

Schedule of Supplemental Cash Flow Information

	Year Ended December 31,
	2020		2019		2018
	(in millions of dollars)
Interest paid	$	29.4	$	23.6	$	21.6
Non-cash investing and financing activities (included in Accounts payable):
Unpaid purchases of property and equipment	$	4.5	$	4.5	$	7.0
Stock repurchases not yet settled	$	—	$	—	$	1.3
Supplemental lease disclosures:
Operating lease liabilities arising from obtaining operating lease assets	$	5.4	$	1.8	n/a
Cash paid for amounts included in the measurement of    operating lease liabilities	$	4.5	$	3.8	n/a
Finance lease liabilities arising from obtaining finance lease assets	$	3.2	$	1.0	$	6.5
	As of December 31,
	2020		2019		2018
Components of cash, cash equivalents and restricted cash:
Cash and cash equivalents	$	780.3	$	264.3	$	125.6
Restricted cash included in Prepaid expenses and other current assets		—		0.3		0.3
Restricted cash included in Other assets		14.0		14.0		13.7
Total cash, cash equivalents and restricted cash shown in our Statements of    Consolidated Cash Flows	$	794.3	$	278.6	$	139.6