Fair value of financial instruments (Tables)

12 Months Ended

Dec. 31, 2020

Fair value of financial instruments

Schedule of estimated carrying values and fair values of financial instruments

	December 31,
	2020				2019
	Carrying				Carrying
	Amount		Fair Value		Amount		Fair Value
Long-term debt, including current portion	$	487.2	$	539.0	$	560.4	$	589.5
Convertible debentures		90.3		94.6		88.5		93.0

Schedule of recurring measurements of fair value hierarchy of financial assets and liabilities

	December 31, 2020
	Level 1		Level 2		Level 3		Total
Assets:
Cash and cash equivalents	$	38.8	$	—	$	—	$	38.8
Restricted cash		7.1		—		—		7.1
Derivative instruments asset		—		0.4		—		0.4
Total	$	45.9	$	0.4	$	—	$	46.3
Liabilities:
Derivative instruments liability	$	—	$	17.6	$	1.5	$	19.1
Total	$	—	$	17.6	$	1.5	$	19.1

	December 31, 2019
	Level 1		Level 2		Level 3		Total
Assets:
Cash and cash equivalents	$	74.9	$	—	$	—	$	74.9
Restricted cash		7.7		—		—		7.7
Derivative instruments asset		—		0.7		—		0.7
Total	$	82.6	$	0.7	$	—	$	83.3
Liabilities:
Derivative instruments liability	$	—	$	24.7	$	3.2	$	27.9
Total	$	—	$	24.7	$	3.2	$	27.9

Schedule of FVM of conversion option derivative

	Fair value Measurement Using Significant Unobservable Inputs (Level 3)
	Year Ended
	December 31, 2020
Beginning balance of liability at January 1, 2020	$	3.2
Total unrealized gain		(1.8)
Currency translation loss		0.1
Ending balance of liability at December 31, 2020	$	1.5