Income taxes (Tables)

6 Months Ended

Jun. 30, 2020

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

	Three Months Ended June 30,					Six Months Ended June 30,
	2020			2019		2020			2019
Continuing operations
Provision (benefit) for income taxes (in millions)	$	(43.2	)	12.7		$	(55.4	)	22.4
Effective tax rate	158.8		%	47.4	%	151.4		%	43.9	%