Income Tax (Reconciliation of Income Tax Provision between US Statutory Rate and As Reported for Continuing Operations) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income tax expense benefit continuing operations income tax reconciliation
Tax provision at U.S. statutory rate			$ 1,238	$ 1,498	$ 1,977
Dividend received deduction			(67)	(69)	(71)
Tax-exempt income			(97)	(86)	(70)
Prior year tax (1)			(27)	(13)	559
Low income housing tax credits			(278)	(270)	(221)
Other tax credits			(102)	(98)	(67)
Foreign tax rate differential			(95)	(332)	(555)
Change in valuation allowance			(8)	(9)	5
Other, net			25	72	33
Provision for income tax expense (benefit)			(1,470)	693	1,590
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount					(41)
Possible Change in Tax Assessment [Member]
Income tax expense benefit continuing operations income tax reconciliation
Provision for income tax expense (benefit)	$ 557				557
Foreign Tax Authority
Income tax expense benefit continuing operations income tax reconciliation
Foreign tax rate differential			350
Tax charge related to future repatriation of earnings		$ 444
Undistributed Earnings of Foreign Subsidiaries			3,000
JAPAN
Income tax expense benefit continuing operations income tax reconciliation
Foreign tax rate differential				110	174
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount					57
CHILE
Income tax expense benefit continuing operations income tax reconciliation
Foreign tax rate differential					61
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount				19
ARGENTINA
Income tax expense benefit continuing operations income tax reconciliation
Foreign tax rate differential					31
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount					23
Impact of U.S. Tax Reform
Income tax expense benefit continuing operations income tax reconciliation
Tax provision at U.S. statutory rate			(101)
Provision for income tax expense (benefit)			(1,620)
Deferred Tax Liabilities, Undistributed Foreign Earnings			170
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount			(1,519)	0	0
Impact of U.S. Tax Reform | Foreign Tax Authority
Income tax expense benefit continuing operations income tax reconciliation
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount			170
Impact of U.S. Tax Reform, including US Statutory impact [Member]
Income tax expense benefit continuing operations income tax reconciliation
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount			(1,600)
Impact of Separation [Member]
Income tax expense benefit continuing operations income tax reconciliation
Provision for income tax expense (benefit)			(927)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount			(540)	$ 0	$ 0
Foreign dividends [Member]
Income tax expense benefit continuing operations income tax reconciliation
Tax benefit on dividends from non-us operations			264
Foreign dividends [Member] | Foreign Tax Authority
Income tax expense benefit continuing operations income tax reconciliation
Foreign tax rate differential			$ 180