Employee Benefits (Details 5)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Weighted-average rates to determine net postretirement benefit cost
Discount rate	4.75%	5.25%	5.75%
Expected return on plan assets	7.75%	8.25%	8.25%
Assumptions regarding healthcare cost trend rates
Rate to which the cost trend rate is assumed to decline	5.00%	5.00%
Year that the rate reaches the ultimate trend rate	2019	2019
Common Trust Funds [Member]
Asset target allocation ranges prescribed by the trusts' investment policies
Equity securities, minimum	70.00%
Equity securities, maximum	90.00%
Fixed income securities, minimum	0.00%
Fixed income securities, maximum	10.00%
Convertible securities, minimum	0.00%
Convertible securities, maximum	10.00%
Cash equivalents and other assets, minimum	10.00%
Cash equivalents and other assets, maximum	30.00%
Under Age 65 [Member]
Assumptions regarding healthcare cost trend rates
Healthcare cost trend rate assumed for the next year	8.50%	8.00%
Age 65 and Over [Member]
Assumptions regarding healthcare cost trend rates
Healthcare cost trend rate assumed for the next year	0.00%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Weighted-average rates to determine net postretirement benefit cost
Discount rate	4.75%	5.25%	5.75%
Expected return on plan assets	5.45%	5.46%	5.48%

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Defined benefit plan maximum target allocation percentage of assets convertible securities.

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Defined Benefit Plan Maximum Target Allocation Percentage Of Cash equivalents and Assets Other.

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Defined benefit plan minimum target allocation percentage of assets convertible securities.

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Defined Benefit Plan Minimum Target Allocation Percentage Of Cash equivalents and Assets Other.

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- Definition

The interest rate used to adjust for the time value of money.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 264

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

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-Name Statement of Financial Accounting Standard (FAS)

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The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

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-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

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- Definition

Target allocation maximum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation minimum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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-Name Statement of Financial Accounting Standard (FAS)

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Target allocation maximum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation minimum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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- Definition

The ultimate trend rate for health care costs.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

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The year when the ultimate health care cost trend rate is expected to be reached.

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-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

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