Consolidated Statements of Shareholders' Equity (Unaudited) (Parenthetical) (USD $) In Millions	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010
Income tax benefit on unrealized (loss) on marketable securities	$ 0	$ 4
Income tax benefit on unrecognized prior service cost	0	1
Accumulated Other Comprehensive Income
Income tax benefit on unrealized (loss) on marketable securities	0	4
Income tax benefit on unrecognized prior service cost	$ 0	$ 1

Tax effect on the cost of benefit improvement resulting from a plan amendment that occurred during the period. The cost has not been recognized in net periodic benefit cost pursuant to FAS 87 and 106. A plan amendment includes provisions that grant increased benefits based on services rendered in prior periods.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph c(3)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 158
-Paragraph 7
-Subparagraph a

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 25

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