Fair Value Measurements, Other Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Financial assets:
Cash and temporary cash investments, at carrying amount	$ 5,176	$ 4,816	$ 5,949	$ 4,114
Financial liabilities:
Debt (excluding capital leases), at carrying amount	7,930	7,926
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and temporary cash investments, at fair value	5,176	4,816
Fair Value, Inputs, Level 2 [Member]
Financial liabilities:
Debt (excluding capital leases), at fair value	$ 9,195	$ 8,882