Schedule II - Condensed Financial Information, Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 2,771	$ 2,972	$ 4,155	$ 3,185
Short-term investments	245	199
Other assets	2,720	2,316
Total assets	63,141	61,759
Liabilities:
Short-term debt	110	240
Long-term debt	5,191	5,199
Total liabilities	48,897	47,999
Shareholders Equity:
Common stock (shares issued, 296; authorized, 600)	74	74
Additional paid-in capital	2,963	2,940
Accumulated other comprehensive loss	(1,547)	(1,082)
Retained earnings	16,933	15,800
Less: treasury stock, at cost	(4,228)	(4,021)
Total shareholders' equity	14,195	13,711
Total liabilities and equity	$ 63,141	$ 61,759