Fair Value Measurements, Other Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Financial assets:
Cash and temporary cash investments, at carrying amount	$ 5,301	$ 3,689	$ 4,191	$ 4,292
Financial liabilities:
Debt (excluding capital leases), at carrying amount	7,293	6,354
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and temporary cash investments, at fair value	5,301	3,689
Fair Value, Inputs, Level 2 [Member]
Financial liabilities:
Debt (excluding capital leases), at fair value	$ 8,117	$ 7,562