Schedule II - Condensed Financial Information, Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 1,968	$ 1,420	$ 2,795	$ 2,978
Short-term investments	381	163
Other assets	2,476	2,657
Total assets	57,088	55,870
Liabilities:
Short-term debt	149	147
Long-term debt, carrying value	5,020	4,979
Total liabilities	44,975	44,991
Shareholders Equity:
Common stock (shares issued, 296; authorized, 600)	74	74
Additional paid-in capital	2,859	2,769
Accumulated other comprehensive loss	(1,250)	(936)
Retained earnings	12,121	10,289
Less treasury stock, at cost	(1,769)	(1,422)
Total shareholders' equity	12,035	10,774
Total liabilities and equity	57,088	55,870
Parent Company [Member]
Assets
Cash and cash equivalents	16	51	$ 0	$ 115
Short-term investments	54	0
Investments in subsidiaries	18,799	17,645
Intercompany	182	74
Other assets	497	526
Total assets	19,548	18,296
Liabilities:
Intercompany	1,086	1,138
Short-term debt	100	100
Long-term debt, carrying value	4,910	4,858
Other liabilities	1,417	1,426
Total liabilities	7,513	7,522
Shareholders Equity:
Common stock (shares issued, 296; authorized, 600)	74	74
Additional paid-in capital	2,859	2,769
Accumulated other comprehensive loss	(1,250)	(936)
Retained earnings	12,121	10,289
Less treasury stock, at cost	(1,769)	(1,422)
Total shareholders' equity	12,035	10,774
Total liabilities and equity	$ 19,548	$ 18,296