Revenue from contracts (Tables)

6 Months Ended

Jun. 30, 2020

Revenue from contracts

Schedule of disaggregation of revenue

	Three Months Ended June 30, 2020
									Consolidated
	Solid Fuel		Natural Gas		Hydroelectric		Corporate		Total
Project revenue:
Energy sales	$	9.4	$	4.8	$	16.9	$	—	$	31.1
Energy capacity revenue		7.8		19.3		—		—		27.1
Steam energy and capacity revenue		—		1.8		—		—		1.8
Waste heat revenue		0.1		—		—		—		0.1
Ancillary and transmission services		—		0.2		—		—		0.2
Asset management and operation		—		—		—		0.2		0.2
Miscellaneous revenue		—		0.8		1.0		—		1.8
		17.3		26.9		17.9		0.2		62.3

	Three Months Ended June 30, 2019
										Consolidated
		Solid Fuel		Natural Gas		Hydroelectric		Corporate		Total
Project revenue:
Energy sales	$	7.9	$	6.9	$	21.7	$	—	$	36.5
Energy capacity revenue		10.7		20.9		—		—		31.6
Steam energy and capacity revenue		—		(0.7)		—		—		(0.7)
Ancillary and transmission services		—		3.2		0.8		—		4.0
Asset management and operation		—		—		—		0.2		0.2
Miscellaneous revenue		—		(0.3)		—		—		(0.3)
		18.6		30.0		22.5		0.2		71.3

	Six Months Ended June 30, 2020
										Consolidated
	Solid Fuel		Natural Gas		Hydroelectric			Corporate		Total
Project revenue:
Energy sales	$	26.1	$	11.0	$	34.6	$		—	$	71.7
Energy capacity revenue		14.1		41.0		—			—		55.1
Steam energy and capacity revenue		—		4.3		—			—		4.3
Waste heat revenue		0.4		—		—			—		0.4
Ancillary and transmission services		—		0.4		—			—		0.4
Asset management and operation		—		—		—			0.5		0.5
Miscellaneous revenue		—		1.0		1.6			—		2.6
		40.6		57.7		36.2			0.5		135.0

	Six Months Ended June 30, 2019
										Consolidated
		Solid Fuel		Natural Gas		Hydroelectric		Corporate		Total
Project revenue:
Energy sales	$	18.2	$	15.9	$	39.4	$	—	$	73.5
Energy capacity revenue		20.0		41.8		—		—		61.8
Steam energy and capacity revenue		—		(0.1)		—		—		(0.1)
Ancillary and transmission services		—		7.3		1.6		—		8.9
Asset management and operation		—		—		—		0.5		0.5
Miscellaneous revenue		0.1		(0.4)		—		—		(0.3)
		38.3		64.5		41.0		0.5		144.3