Available-For-Sale Investments (Reconciliation Of The Changes In Credit Losses Recognized In Earnings) (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Mar. 31, 2011	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010
Available-For-Sale Investments
Beginning balance of credit losses	$ 4	$ 2	$ 4	$ 2
Additions for credit losses not previously recognized in earnings	0	0	1	1
Ending balance of credit losses	$ 4	$ 2	$ 5	$ 3

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
-Section 04
-Paragraph 11
-Article 9

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