Income Tax (Impact of U.S. Tax Reform) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income (loss) before provision for income tax and equity in earnings of subsidiaries	$ 6,927	$ 6,795	$ 6,307
Deferred Federal Income Tax Expense (Benefit)	(115)	(235)	342
Provision for income tax expense (benefit)	1,509	886	1,179
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	5,418	5,909	5,128
Income tax (expense) benefit related to items of other comprehensive income (loss)	1,237	3,324	(1,754)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 74,817	66,382	52,958	$ 58,870
Impact of U.S. Tax Reform
Income (loss) before provision for income tax and equity in earnings of subsidiaries		0	(58)
Deferred Tax Liabilities, Undistributed Foreign Earnings		(317)	468
Deferred Federal Income Tax Expense (Benefit)		(9)	(402)
Provision for income tax expense (benefit)		(326)	66
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		326	(124)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ 326	$ (124)