Investments And Fair Value Measurements (Short-Term Investments By Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets Sold under Agreements to Repurchase [Line Items]
Short-term investments	$ 3,718	$ 4,328
Due In One Year Or Less [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term investments	2,904
Due Between One Year And Three Years [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term investments	312
Due After Three Years [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term investments	$ 502