Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended						9 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2011 Predecessor	Dec. 31, 2010 Predecessor
Current tax provision (benefit):
Federal							$ 2	$ 22		$ (1)	$ (14)
State and local							2			1	11
Total current tax (benefit) provision							4	22			(3)
Deferred tax provision:
Federal							24	155		120	470
State and local							4	19		26	38
Total deferred tax expense							27	174		145	508
Income tax expense	67	54	27	48	(1)	33	32	196	178	146	505
Valuation allowance
Increase (decrease) in total valuation allowance							7	4		1	7
Increase in income tax expense								18	(327)
Effective income tax rate:
Federal statutory income tax rate (as a percent)							35.00%	35.00%		35.00%	35.00%
State income taxes-net of federal effect and tax expense (benefit) of income (loss) not recognized (as a percent)							5.30%	2.50%		4.80%	9.00%
Medicare subsidy, including effect of 2010 Health Care Legislation (as a percent)							(1.50%)	(0.10%)			22.80%
Loss on embedded option in convertible debt (as a percent)											37.00%
Excess compensation (as a percent)											4.30%
Merger-related costs (as a percent)											1.70%
Uncertain tax position changes (as a percent)							(1.10%)			0.20%
Disallowed meals and entertainment (as a percent)							4.20%	0.20%		0.20%	0.50%
Foreign tax expense (as a percent)							2.50%	0.80%
Other (as a percent)							3.70%	0.50%		0.50%	1.20%
Adjustments related to prior periods (as a percent)											(0.60%)
Changes in valuation allowance (as a percent)							15.30%			0.10%	1.30%
Effective income tax rate (as a percent)							63.40%	38.90%		40.80%	112.20%
Deferred tax assets:
Net operating loss carryforwards	1,973				2,437		2,437	1,973	2,437
Post-retirement and pension benefit costs	1,506				1,296		1,296	1,506	1,296
Deferred loss subject to amortization	244				260		260	244	260
Debt related differences	154				258		258	154	258
Other employee benefits	110				97		97	110	97
Other	422				521		521	422	521
Gross deferred tax assets	4,409				4,869		4,869	4,409	4,869
Valuation allowance on deferred tax assets	(260)				(256)		(256)	(260)	(256)		(139)
Net deferred tax assets	4,149				4,613		4,613	4,149	4,613
Deferred tax liabilities:
Property, plant and equipment and intangible assets	(1,817)				(1,512)		(1,512)	(1,817)	(1,512)
Intangibles	(2,163)				(2,963)		(2,963)	(2,163)	(2,963)
Other	(190)				(209)		(209)	(190)	(209)
Total deferred tax liabilities	(4,170)				(4,684)		(4,684)	(4,170)	(4,684)
Net deferred tax (liability) assets	(21)				(71)		(71)	(21)	(71)
Reconciliation of the unrecognized tax benefits
Balance at the beginning of the period				64				64	203
Additions for prior year tax positions									3
Reductions for prior year tax positions								(34)	(1)
Settlements									(141)
Balance at the end of the period	30				64		64	30	64
Additional information
Interest expense and penalties recognized related to income taxes							1			1
Liabilities recorded for interest related to uncertain tax positions	$ 28				$ 28		$ 28	$ 28	$ 28