Basis of Presentation and Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Accounting Policies [Line Items]
Current	$ 191		$ 191		$ 203
Non-current	66		66		69
Total	257		257		272
Cash and cash equivalents subject to project finance facilities and lease agreements	156		156		292
Interest Costs Capitalized	6	12	12	24
Treasury Stock, Value, Acquired, Cost Method			297
Adjustments Related to Tax Withholding for Share-based Compensation			8
Debt Service
Accounting Policies [Line Items]
Current	13		13		11
Non-current	41		41		41
Total	54		54		52
Rent Reserve
Accounting Policies [Line Items]
Current	4		4		3
Non-current	0		0		0
Total	4		4		3
Construction Major Maintenance
Accounting Policies [Line Items]
Current	35		35		35
Non-current	20		20		20
Total	55		55		55
Security Project Insurance
Accounting Policies [Line Items]
Current	139		139		151
Non-current	3		3		6
Total	142		142		157
Other
Accounting Policies [Line Items]
Current	0		0		3
Non-current	2		2		2
Total	$ 2		$ 2		$ 5
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			59 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			47 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			47 years