Income taxes (Tables)

9 Months Ended

Sep. 30, 2016

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016			2015
Continuing operations
Provision for income taxes (in millions)	$	19.5		14.1		$	43.4		37.2
Effective tax rate	43.0		%	65.9	%	60.1		%	341.3	%