Income taxes (Tables)

9 Months Ended

Sep. 30, 2015

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

	Three Months Ended September 30,					Nine Months Ended September 30,
	2015			2014		2015		2014
Continuing operations
Provision for income taxes (in millions)	$	14.1		26.8		37.2		39.6
Effective tax rate	65.9		%	48.7	%	341.3	%	(187.7	%)