Schedule II - Condensed Financial Information, Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 3,185	$ 1,968	$ 1,420	$ 2,795
Short-term investments	691	381
Other assets	2,227	2,476
Total assets	59,360	57,088
Liabilities:
Short-term debt	276	149
Long-term debt, carrying value	4,756	5,020
Total liabilities	45,575	44,975
Shareholders Equity:
Common stock (shares issued, 296; authorized, 600)	74	74
Additional paid-in capital	2,892	2,859
Accumulated other comprehensive loss	(1,382)	(1,250)
Retained earnings	13,855	12,121
Less: treasury stock, at cost	(1,716)	(1,769)
Total shareholders' equity	13,723	12,035
Total liabilities and equity	59,360	57,088
Parent Company [Member]
Assets
Cash and cash equivalents	18	16	$ 51	$ 0
Short-term investments	57	54
Investments in subsidiaries	20,315	18,799
Intercompany	173	182
Other assets	415	497
Total assets	20,978	19,548
Liabilities:
Intercompany	998	1,086
Short-term debt	257	100
Long-term debt, carrying value	4,658	4,910
Other liabilities	1,342	1,417
Total liabilities	7,255	7,513
Shareholders Equity:
Common stock (shares issued, 296; authorized, 600)	74	74
Additional paid-in capital	2,892	2,859
Accumulated other comprehensive loss	(1,382)	(1,250)
Retained earnings	13,855	12,121
Less: treasury stock, at cost	(1,716)	(1,769)
Total shareholders' equity	13,723	12,035
Total liabilities and equity	$ 20,978	$ 19,548