Income Taxes (Deferred Income Tax Assets (Liabilities)) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Pension and other postretirement benefits	$ 682	$ 883
Tax credits and loss carryforwards	443	538
Other	599	667
Deferred Tax Assets, Gross	1,724	2,088
Valuation allowance	(274)	(215)
Total deferred tax assets	1,450	1,873
Pension and other postretirement benefits	254	260
Property, plant and equipment, net	1,118	1,162
Investments in subsidiaries	186	223
Other	281	339
Total deferred tax liabilities	1,839	1,984
Net deferred tax assets (liabilities)	$ (389)	$ (111)