Segment Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Segment information
Number of operating segments	3
Expenses	$ 3,947	$ 1,249	$ 5,179	$ 2,504
Net income	459	523	923	1,068
Operating segments
Segment information
Revenues	4,153	1,633	5,714	3,295
Expenses	1,828	594	2,409	1,190
Net income	2,325	1,039	3,305	2,105
Margin percentage (as a percent)	56.00%	64.00%	58.00%	64.00%
Regional Markets
Segment information
Revenues	2,256	1,165	3,374	2,352
Expenses	973	432	1,404	875
Net income	1,283	733	1,970	1,477
Margin percentage (as a percent)	57.00%	63.00%	58.00%	63.00%
Business Markets
Segment information
Revenues	922	67	986	134
Expenses	551	31	580	59
Net income	371	36	406	75
Margin percentage (as a percent)	40.00%	54.00%	41.00%	56.00%
Wholesale Markets
Segment information
Revenues	975	401	1,354	809
Expenses	304	131	425	256
Net income	$ 671	$ 270	$ 929	$ 553
Margin percentage (as a percent)	69.00%	67.00%	69.00%	68.00%

Represents the number of operating segments of the entity.

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- Definition

Represents the operating margin assigned to segments for the period.

+ Details

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- Definition

Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

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.

+ References

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

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