Income taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Components of income tax expenses (benefit)
Current income tax expense	$ 1.4	$ 0.3	$ 2.3	$ 1.8
Deferred income tax benefit	(23.7)	(18.7)	(24.9)	(18.6)
Total income tax benefit, net	$ (22.3)	$ (18.4)	$ (22.6)	$ (16.8)
Reconciliation of income taxes
Canadian enacted statutory rate (as a percent)	26.00%	26.00%	26.00%	26.00%
Computed income taxes at 26% Canadian statutory rate	$ 11.0	$ 9.0	$ 11.2	$ 12.0
Operating in higher tax rate jurisdictions	8.4		8.7
Change in valuation allowance	2.6	1.8	1.9	4.6
Return to provision adjustments	0.2		0.3
Foreign exchange	0.6	2.6	1.0	5.1
Capital gain on intercompany notes		4.6		4.2
Other permanent differences		0.4	0.1	0.1
Capital loss on intercompany notes		18.8
Capital losses on tax restructuring		$ 18.8		$ 18.8
Valuation allowance	$ 184.1		$ 184.1

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to capital losses on intercompany notes.

No definition available.