Retirement, Other Postretirement Benefits, and Defined Contribution Plans (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011 PensionPlans Y	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 1992
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations				$ 241,400,000
Accumulated benefit obligation	4,600,000,000	3,800,000,000
Defined benefit pension plan liability	3,133,657,000	2,175,364,000
Current liabilities	44,031,000	39,862,000
Unamortized transition asset, Prior service cost and Net loss recognized in accumulated comprehensive income before tax	554,261,000	299,948,000
Retirement Other Postretirement Benefits And Defined Contribution Plans (Textual) [Abstract]
Mandatory employee contribution under Retirement Plan.	3.00%
Number of qualified pension plans	7
Voluntary employee contributions contribution under Retirement Plan	1% to 10% of earnings for a limited group of employees
No of years in plan participation	10 years
Maximum contribution from earnings by employees	10.00%
Minimum contribution from earnings by employees	1.00%
Period of Amortization of Accumulated Postretirement Benefit Obligations	20
Period of Amortization of Regulatory asset	15
Expected 2012 pension contributions	163,000,000
Expected 2012 postretirement contributions	80,400,000
Medicare subsidies for prescription drug claims received	4,600,000
Reduction in Accumulated postretirement Benefit Obligation (APBO)	274,000,000	267,000,000
Non qualified pension cost	24,000,000	27,200,000	23,600,000
Reduction in other postretirement benefit cost	33,000,000	26,600,000	24,000,000
Settlement charge related to the payment of lump sum benefits out of plan	4,600,000	9,300,000	6,700,000
Employers contribution to defined contribution plan as percentage of employees contribution	70.00%
Employers contribution to defined contribution plan as percentage of eligible earnings per pay period	6.00%
Subsidiaries' contribution to defined contribution plan	42,600,000	41,800,000	41,900,000
Domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Equity Securities, Target	39.00%
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Equity Securities, Target	26.00%
Qualified Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations				128,000,000
Accumulated benefit obligation	146,500,000	131,600,000
Projected benefit obligation	5,187,635,000	4,301,218,000	3,837,744,000
Defined benefit pension plan liability	(1,787,719,000)	(1,084,950,000)
Other Postretirement Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed health care cost trend rate used in measuring Net Other Postretirement Benefit Cost for post-65 retirees for 2011	8.50%
Ultimate healthcare cost trend rate	4.75%
Projected benefit obligation	1,652,369,000	1,386,370,000	1,280,076,000
Defined benefit pension plan liability	(1,192,365,000)	(951,715,000)
Current liabilities	(32,832,000)	(30,225,000)
Unamortized transition asset, Prior service cost and Net loss recognized in accumulated comprehensive income before tax	247,823,000	150,783,000
Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan liability	153,200,000	138,700,000
Current liabilities	11,200,000	9,600,000
Unamortized transition asset, Prior service cost and Net loss recognized in regulatory assets	58,900,000	53,500,000
Unamortized transition asset, Prior service cost and Net loss recognized in accumulated comprehensive income before tax	$ 27,200,000	$ 24,300,000
Pre-65 retirees [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed health care cost trend rate used in measuring Net Other Postretirement Benefit Cost for post-65 retirees for 2011	7.75%
Ultimate healthcare cost trend rate	4.75%
Post-65 retirees [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed health care cost trend rate used in measuring Net Other Postretirement Benefit Cost for post-65 retirees for 2011	7.50%
Ultimate healthcare cost trend rate	4.75%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fixed Income Securities, Target	35.00%
Other Postretirement Trusts beyond for pre-65 Retirees [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed health care cost trend rate used in measuring Net Other Postretirement Benefit Cost for post-65 retirees for 2011	8.00%