Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
State net operating losses	$ 5	$ 294
Foreign net operating losses	2	23
Federal net operating loss	44	1,466
Compensation programs	56	145
Allowance for doubtful accounts	10	89
Self-insurance reserves	7	16
Accrued restructuring and support expenses	317	0
Accrued expenses	6	52
Federal tax credits	35	52
Federal indirect tax benefits of uncertain state tax positions	0	1
Investment in CGP LLC	115	0
Investments in non-consolidated affiliates	0	28
Capital loss carryover	15	134
Deferred revenue	1	93
Subtotal	613	2,393
Less: valuation allowance	207	970
Total deferred tax assets	406	1,423
Depreciation and other property-related items	922	1,143
Deferred cancellation of debt income and other debt-related items	152	1,508
Investment in CGP	0	21
Investment in non-consolidated affiliates	170	0
Intangibles	111	998
Prepaid expenses	10	28
Other	4	2
Total deferred tax liabilities	1,369	3,700
Net deferred tax liability	$ 963	$ 2,277