CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	$ 1.0	$ (19.8)	$ 15.1	$ (20.3)
Other comprehensive (loss) income, net of tax:
Unrealized gain (loss) on hedging activities		(0.1)	0.2	(0.3)
Net amount reclassified to earnings	0.1	0.1	0.2	0.4
Net unrealized gain on derivatives	0.1		0.4	0.1
Defined benefit plan, net of tax				0.1
Foreign currency translation adjustments	(2.9)	4.7	(7.5)	6.7
Other comprehensive (loss) income, net of tax	(2.8)	4.7	(7.1)	6.9
Comprehensive (loss) income	(1.8)	(15.1)	8.0	(13.4)
Less: Comprehensive income (loss) attributable to preferred shares of a subsidiary company	1.6	2.1	(0.1)	4.3
Comprehensive (loss) income attributable to Atlantic Power Corporation	$ (3.4)	$ (17.2)	$ 8.1	$ (17.7)