Income taxes (Tables)

9 Months Ended

Sep. 30, 2019

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

	Three Months Ended September 30,					Nine Months Ended September 30,
	2019			2018		2019			2018
Continuing operations
Provision for income taxes (in millions)	$	14.7		23.0		$	37.1		53.0
Effective tax rate	67.4		%	54.9	%	51.0		%	(514.6	%)