Condensed Financial Information (Parent Company) (Basis of Presentation Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Assets	$ 719,892	$ 898,764
Retained Earnings (Accumulated Deficit)	26,527	34,683	$ 35,672	$ 32,110
Accumulated Other Comprehensive Income (Loss), Net of Tax	7,427	5,366	4,767	10,714
Stockholders' Equity Attributable to Parent	58,676	67,531	68,098	72,208
Liabilities and Equity	719,892	898,764
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Investments in and Advances to Affiliates, at Fair Value	73,274	85,429
Assets	81,091	93,107
Retained Earnings (Accumulated Deficit)	26,527	34,683
Accumulated Other Comprehensive Income (Loss), Net of Tax	7,427	5,366
Stockholders' Equity Attributable to Parent	58,676	67,531
Liabilities and Equity	$ 81,091	93,108
Scenario, Previously Reported
Condensed Balance Sheet Statements, Captions [Line Items]
Retained Earnings (Accumulated Deficit)		34,480	35,519	32,020
Accumulated Other Comprehensive Income (Loss), Net of Tax		5,347
Stockholders' Equity Attributable to Parent		67,309	67,949	72,053
Scenario, Previously Reported | Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Investments in and Advances to Affiliates, at Fair Value		85,207
Assets		92,885
Retained Earnings (Accumulated Deficit)		34,480
Accumulated Other Comprehensive Income (Loss), Net of Tax		5,347
Stockholders' Equity Attributable to Parent		67,309
Liabilities and Equity		92,886
Restatement Adjustment
Condensed Balance Sheet Statements, Captions [Line Items]
Retained Earnings (Accumulated Deficit)		203	153	90
Accumulated Other Comprehensive Income (Loss), Net of Tax		19
Stockholders' Equity Attributable to Parent		222	$ 149	$ 155
Restatement Adjustment | Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Investments in and Advances to Affiliates, at Fair Value		222
Assets		222
Retained Earnings (Accumulated Deficit)		203
Accumulated Other Comprehensive Income (Loss), Net of Tax		19
Stockholders' Equity Attributable to Parent		222
Liabilities and Equity		$ 222