Available-For-Sale Investments (Reconciliation Of The Changes In Credit Losses Recognized In Earnings) (Details) (USD $) In Millions	3 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2009
Available-For-Sale Investments
Beginning balance of credit losses	$ 4	$ 2	$ 5	$ 4	$ 3	$ 2
Additions for credit losses not previously recognized in earnings	1	1
Ending balance of credit losses	$ 5	$ 3	$ 5	$ 4	$ 3	$ 2

Periodic provision charged to earnings, based on an assessment of credit risk, the offset to which is either added to or deducted from the allowance account for the purpose of reducing receivable, other than loans and leases, to an amount that approximates their net realizable value (amount expected to be collected).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 9

-Section 04

-Paragraph 11

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Name:	us-gaap_ProvisionForOtherCreditLosses
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration