Income Taxes - Components of Current and Noncurrent Deferred Tax Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current:
Gross deferred tax assets	$ 2,006	$ 1,819
Gross deferred tax liabilities	(928)	(984)
Valuation allowance	(126)	(211)
Total deferred tax assets	1,880	1,608
Total deferred tax liabilities	(928)	(984)
Current assets
Current:
Accounts and notes receivable	59	96
Inventory	73	73
Accrued expenses	305	311
Deferred revenue	472	365
Equity	148	83
Net operating losses	23	28
Total current	1,101	960
Deferred Tax Assets, Tax Credit Carryforwards	21	4
Noncurrent assets
Current:
Deferred revenue	346	253
Net operating losses	93	78
Deferred Tax Assets, Other	23	0
Deferred Tax Liabilities, Equity Adjustments	(106)	(139)
Deferred Tax Assets, Tax Credit Carryforwards	234	280
Other comprehensive loss	103	109
Deferred Tax Assets, Gross, Noncurrent	905	859
Noncurrent liabilities
Current:
Property, plant and equipment, net	(323)	(291)
Intangible and other assets, net	(605)	(680)
Other non-current liabilities	0	(13)
Deferred Tax Liability, Total noncurrent	$ (928)	$ (984)