Subsequent Event (Details) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011 Wilson Distribution Business [Member]	Apr. 10, 2012 Wilson Distribution Business [Member]
Subsequent Events (Textual)
Divestiture of Wilson distribution business				$ 800,000,000
Revenue generated by Wilson distribution business	$ 10,611,000,000	$ 8,716,000,000	$ 2,100,000,000

Amount of total revenue for the reportable segments, including revenue from external customers, transactions with other operating segments of the same entity, and (gross) interest revenue. All considered to be "operating revenue" for purposes of the taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 27

-Subparagraph a, b, c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 22

-Subparagraph (a),(b),(c)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8736-108599

Name:	us-gaap_SegmentReportingInformationRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration