Income Taxes (Deferred Income Tax Assets (Liabilities)) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Pension and other postretirement benefits	$ 499	$ 682
Tax credits and loss carryforwards	450	443
Share based compensation	86	82
Other	512	517
Deferred Tax Assets, Gross	1,547	1,724
Valuation allowances	(225)	(274)
Total deferred tax assets	1,322	1,450
Pension and other postretirement benefits	15	254
Property, plant and equipment, net	1,079	1,118
Investments in subsidiaries	190	186
Goodwill	83	64
Other	253	217
Total deferred tax liabilities	1,620	1,839
Net deferred tax assets (liabilities)	$ (298)	$ (389)