Income taxes (Tables)

6 Months Ended

Jun. 30, 2019

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

	Three Months Ended June 30,					Six Months Ended June 30,
	2019			2018		2019			2018
Continuing operations
Provision for income taxes (in millions)	$	12.7		18.6		$	22.4		30.0
Effective tax rate	47.4		%	(20.9	)%	43.9		%	(57.5	%)