Inventory (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Inventory Disclosure [Abstract]
Raw materials	$ 1,082	$ 955
Work-in-process	343	428
Finished goods	1,229	1,115
Inventory at FIFO	2,654	2,498
Excess of FIFO over LIFO cost	(120)	(116)
Total inventory	$ 2,534	$ 2,382