Fair Value Measurement (Additional Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Impaired Long-Lived Assets Held and Used [Line Items]
Asset write-offs	$ 53
Level 3 [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Long-lived assets carrying amount	10
Long-lived assets fair value amount	7
Asset write-offs	$ 3