Income taxes (Tables)

6 Months Ended

Jun. 30, 2016

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

	Three Months Ended June 30,					Six Months Ended June 30,
	2016			2015		2016			2015
Continuing operations
Provision for income taxes (in millions)	$	14.5		7.6		$	23.9		23.1
Effective tax rate	81.0		%	(40.2	)%	89.2		%	(220.0	%)