Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
NOLs
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions		$ 9	$ 0
Federal
Current		18	1	57
Deferred		305	403	361
State
Current		26	62	15
Deferred		(14)	(8)	33
Foreign
Current		3	9	7
Deferred		0	(4)	0
Total income tax expense		338	463	473
Income tax expense in the consolidated statements of operations:
Attributable to income		338	463	473
Stockholders' equity:
Compensation expense for tax purposes in excess of amounts recognized for financial reporting purposes		(5)	(14)	(18)
Tax effect of the change in accumulated other comprehensive loss		(744)	554	(434)
Reconciliation of the statutory federal income tax rate to effective income tax rate
Statutory federal income tax rate (as a percent)		35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit (as a percent)		2.70%	2.80%	2.50%
Impairments of goodwill (as a percent)		0.00%	188.50%	0.00%
Reversal of liability for unrecognized tax position (as a percent)		0.40%	(24.50%)	0.00%
Foreign income taxes (as a percent)		0.40%	2.70%	0.30%
Nondeductible accounting adjustment for life insurance (as a percent)		0.00%	3.10%	0.00%
Release state valuation allowance (as a percent)		0.00%	(2.30%)	0.00%
Effective income Tax Rate Reconciliation, Foreign Subsidiary Investment Write-Off		(5.40%)	0.00%	0.00%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(2.60%)	1.40%	0.00%
Effective income tax rate (as a percent)		30.50%	206.70%	37.80%
Write-off of investment in foreign subsidiary		60
Impairment of goodwill	1,100	0	1,092	0
Valuation Allowance Reversal			(22)
Expense on reversal of valuation allowance on auction rate securities				(16)
Deferred tax assets
Post-retirement and pension benefit costs		2,276	1,618
Deferred Tax Assets, Operating Loss Carryforwards		1,091	1,532
Other employee benefits		214	182
Other		602	782
Gross deferred tax assets		4,183	4,114
Less valuation allowance		(409)	(435)
Net deferred tax assets		3,774	3,679
Deferred tax liabilities
Property, plant and equipment, primarily due to depreciation differences		(3,869)	(3,904)
Goodwill and other intangible assets		(2,908)	(3,226)
Other		(147)	(137)
Gross deferred tax liabilities		(6,924)	(7,267)
Net deferred tax liabilities		(3,150)	(3,588)
Long-term deferred tax liability		4,030	4,753
Deferred income taxes, net		880	1,165
Summary of reconciliation of the change in gross unrecognized tax benefits activity
Unrecognized tax benefits, beginning of year		14	78
Increase in tax positions taken in the prior year			17
Decrease due to the reversal of tax positions taken in a prior year		(2)	0
Decrease from the lapse of statute of limitations		(1)	(36)
Settlements		(3)	(28)
Unrecognized tax benefits, end of year		17	14	78
Valuation Allowance, Deferred Tax Asset, Change in Amount		26	(5)
State
Reconciliation of the statutory federal income tax rate to effective income tax rate
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount		13
Federal
Reconciliation of the statutory federal income tax rate to effective income tax rate
Refund from taxing authority			$ 33