Income Tax (Impact of U.S. Tax Reform) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 6,795	$ 6,307	$ 3,536
Deferred Federal Income Tax Expense (Benefit)	(235)	342	(2,373)
Income Tax Expense (Benefit)	886	1,179	(1,470)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	5,909	5,128	5,006
Income tax (expense) benefit related to items of other comprehensive income (loss)	3,324	(1,754)	984
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	66,382	52,958	58,870	$ 67,702
Impact of U.S. Tax Reform
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	0	(58)	(289)
Deferred Tax Liabilities, Undistributed Foreign Earnings	(317)	468	170
Deferred Federal Income Tax Expense (Benefit)	(9)	(402)	(1,790)
Income Tax Expense (Benefit)	(326)	66	(1,620)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	326	(124)	1,331
Income tax (expense) benefit related to items of other comprehensive income (loss)	0	0	144
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 326	$ (124)	$ 1,475