Benefit Plans, Defined Contribution Plans (Details) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Number of payments to defined contribution plan	1
Thrift Plan [Member]
Percentage of participants contributions matched by employer	100.00%
Maximum percentage of employee contribution subject to match	6.00%
Employer contribution amount	$ 19,000,000	$ 24,000,000	$ 24,000,000
Treasury stock reissued for benefit plan contributions		13,000,000	8,000,000
Retail Savings Plan [Member]
Maximum percentage of employee contribution subject to match	6.00%
Removed requirement for matching contribution as a percentage	0.5
Employer contribution amount	700,000	100,000	600,000
Treasury stock reissued for benefit plan contributions		100,000	100,000
Non-elective employer contribution	3.00%
Employer contribution match	0.50
Participants contribution matched by employer	$ 1.00

Amount of contributions made by the employer to a defined contribution plan.

No definition available.

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- Definition

Amount employer will contribute to benefit plan to match certain amount of employee contribution.

+ References

No definition available.

+ Details

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- Definition

The maximum employee contribution, as a percentage of an employee's eligible salary that will be subject to the employer contribution match for a defined contribution plan.

+ References

No definition available.

+ Details

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- Definition

Percentage of earnings eligible employees will automatically receive as an employer contribution to a defined contribution benefit plan.

+ References

No definition available.

+ Details

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- Definition

Number of payments made for contributions by employer

+ References

No definition available.

+ Details

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- Definition

Amount of employee contribution to a defined contribution benefit plan of which the employer will match a certain amount.

+ References

No definition available.

+ Details

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- Definition

The percentage of the employee's contributions matched by the employer for contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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- Definition

Value of the treasury stock reissued during the period used to fund employer contributions to employee benefit plans.

+ References

No definition available.

+ Details

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- Definition

Description of the terms and benefits provided by the employer's defined contribution plans. A defined contribution plan provides benefits in return for services rendered, provides an individual account for each participant, and has terms that specify how contributions to the individual's account are to be determined rather than the amount of benefits the individual is to receive. Under a defined contribution pension plan, the benefits a participant will receive depend solely on the amount contributed to the participant's account, the returns earned on investments of those contributions, and forfeitures of other participants' benefits that may be allocated to such participant's account. A description of the plan(s) including employee groups covered, the basis for determining contributions, and the nature and effects of significant matters affecting comparability of information for all periods presented.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Defined Contribution Postretirement Plan

-URI http://asc.fasb.org/extlink&oid=6510416

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 106

-Paragraph 518

-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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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