Retirement and Other Postretirement Benefits (Details) (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Qualified Pension [Member]
Components of Qualified Net Pension Cost and Net Other Postretirement Benefit Cost and Other Amounts Recognized as a Regulatory Asset and/or Accumulated Other Comprehensive Income (AOCI)
Service cost - benefits earned during the period	$ 30,490	$ 26,239	$ 60,980	$ 52,478
Interest cost on accumulated postretirement benefit obligation (APBO)	59,248	57,802	118,496	115,604
Expected return on assets	(75,319)	(64,902)	(150,638)	(129,804)
Amortization of prior service cost (credit)	838	1,164	1,676	2,328
Amortization of loss	23,244	16,475	46,488	32,950
Net pension costs	38,501	36,778	77,002	73,556
Other Postretirement [Member]
Components of Qualified Net Pension Cost and Net Other Postretirement Benefit Cost and Other Amounts Recognized as a Regulatory Asset and/or Accumulated Other Comprehensive Income (AOCI)
Service cost - benefits earned during the period	14,835	13,078	29,670	26,156
Interest cost on accumulated postretirement benefit obligation (APBO)	18,631	19,020	37,262	38,040
Expected return on assets	(7,369)	(6,553)	(14,738)	(13,106)
Amortization of transition obligation	796	932	1,592	1,864
Amortization of prior service cost (credit)	(3,518)	(3,015)	(7,036)	(6,030)
Amortization of loss	5,298	4,317	10,596	8,634
Net pension costs	$ 28,673	$ 27,779	$ 57,346	$ 55,558

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The amount of gains or losses recognized in net periodic benefit cost

+ 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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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
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- Definition

The amount of the transition obligation or asset recognized in net periodic benefit cost.

+ 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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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 106
-Paragraph 518

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 264

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Number 132R
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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

+ References

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph h

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

+ References

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