Schedule II - Condensed Financial Information, Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 3,634	$ 2,972	$ 3,611	$ 3,185
Short-term investments	220	199
Other assets	2,412	2,316
Total assets	63,102	61,759
Liabilities:
Short-term debt	109	240
Long-term debt	5,195	5,199
Total liabilities	48,320	47,999
Shareholders Equity:
Common stock (shares issued, 296; authorized, 600)	74	74
Additional paid-in capital	2,974	2,940
Accumulated other comprehensive loss	(1,843)	(1,082)
Retained earnings	17,722	15,800
Less: treasury stock, at cost	(4,184)	(4,021)
Total shareholders' equity	14,743	13,711
Total liabilities and shareholders' equity	$ 63,102	$ 61,759