Schedule II - Condensed Financial Information, Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Assets
Cash and cash equivalents	$ 3,656	$ 3,185	$ 3,224	$ 1,968
Short-term investments	175	691
Other assets	2,362	2,227
Total assets	61,936	59,360
Liabilities:
Short-term debt	141	276
Long-term debt, carrying value	5,207	4,756
Total liabilities	47,739	45,575
Shareholders Equity:
Common stock (shares issued, 296; authorized, 600)	74	74
Additional paid-in capital	2,929	2,892
Accumulated other comprehensive loss	(1,124)	(1,382)
Retained earnings	15,590	13,855
Less: treasury stock, at cost	(3,324)	(1,716)
Total shareholders' equity	14,145	13,723
Total liabilities and equity	$ 61,936	$ 59,360