Income Taxes Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits, Period Increase (Decrease)									$ 205
Income Tax Provision (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Current income tax benefit (provision)									(2,089)	$ 114	$ 600
Deferred income tax provision									(1,328)	(4,254)	(16,584)
Provision for federal income taxes	$ (865)	$ (1,036)	$ (889)	$ (627)	$ (828)	$ (1,045)	$ (1,136)	$ (1,131)	$ (3,417)	$ (4,140)	$ (15,984)
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Statutory corporate tax rate									21.00%	21.00%	35.00%	35.00%
Equity investments in affordable housing projects									(0.20%)	(0.60%)	(1.40%)
Effect of corporate tax rate change									0.00%	0.00%	53.60%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent									(1.20%)	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent									(0.20%)	0.20%	(0.60%)
Effective tax rate									19.40%	20.60%	86.60%