Fair Value Measurements (Nonrecurring Fair Value Measurements) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 MW	Mar. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Planned capacity of Spain Solar projects - in megawatts	99.8
Carrying value of property, plant, and equipment prior to impairment charge	$ 800
Property, Plant, and Equipment, Fair Value Disclosure	500
Impairment of Long-Lived Assets Held-for-use	300	0
Impairment Of Long Lived Assets Held For Use After Tax	$ 342