Basis of Presentation and Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Accounting Policies [Line Items]
Asset Impairment Charges	$ 0	$ 0	$ 0	$ 0
Gain on Business Interruption Insurance Recovery	8	0	8	0
Prior Period Reclassification Adjustment					$ 152
Current	148		148		216
Non-current	20		20		12
Total	168		168		228
Interest costs capitalized	5	$ 4	9	$ 9
Debt service
Accounting Policies [Line Items]
Current	34		34		28
Non-current	8		8		8
Total	42		42		36
Construction major maintenance
Accounting Policies [Line Items]
Current	36		36		50
Non-current	9		9		2
Total	45		45		52
Security project insurance
Accounting Policies [Line Items]
Current	75		75		136
Non-current	2		2		0
Total	77		77		136
Other
Accounting Policies [Line Items]
Current	3		3		2
Non-current	1		1		2
Total	$ 4		$ 4		$ 4
Geothermal properties, gross [Member] | Minimum [Member]
Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives			13 years
Geothermal properties, gross [Member] | Maximum [Member]
Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives			58 years
Property, plant and equipment, other types [Member] | Minimum [Member]
Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives			3 years
Property, plant and equipment, other types [Member] | Maximum [Member]
Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives			46 years
Building, machinery and equipment, gross [Member] | Minimum [Member]
Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives			3 years
Building, machinery and equipment, gross [Member] | Maximum [Member]
Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives			46 years