Income Tax (Impact of U.S. Tax Reform) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									$ 6,307	$ 3,536	$ 4,281
Deferred Federal Income Tax Expense (Benefit)									342	(2,373)	(827)
Income Tax Expense (Benefit)									1,179	(1,470)	693
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 2,062	$ 915	$ 894	$ 1,257	$ 2,315	$ 883	$ 856	$ 952	5,128	5,006	3,588
Income tax (expense) benefit related to items of other comprehensive income (loss)									(1,754)	984	450
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	52,958				58,870				52,958	58,870	$ 67,702	$ 68,568
Impact of U.S. Tax Reform
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									(58)	(289)
Deferred Tax Liabilities, Undistributed Foreign Earnings	468				170				468	170
Deferred Federal Income Tax Expense (Benefit)									(402)	(1,790)
Income Tax Expense (Benefit)									66	(1,620)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									(124)	1,331
Income tax (expense) benefit related to items of other comprehensive income (loss)									0	144
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (124)				$ 1,475				$ (124)	$ 1,475